Fix uses of 'nil' and 'non-nil' in manuals and a few more minor issues

* doc/emacs/building.texi (Grep Searching): Fix doc of
'grep-save-buffers'.
(Drag and Drop): Reorder paragraphs.  Fix doc of
'mouse-drag-and-drop-region'.
* doc/emacs/frames.texi (Word and Line Mouse):
* doc/emacs/search.texi (Other Repeating Search):
* doc/lispref/compile.texi (Compilation Functions):
* doc/lispref/files.texi (Directory Names):
* doc/lispref/functions.texi (Advising Named Functions):
* doc/lispref/keymaps.texi (Controlling Active Maps):
* doc/lispref/lists.texi (Association Lists):
* doc/lispref/windows.texi (Quitting Windows): Fix uses of
'non-nil' and 'nil'.

doc/emacs/building.texi

@@ -394,10 +394,11 @@ match will be highlighted, instead of the entire source line.
   The @command{grep} commands will offer to save buffers before
 running.  This is controlled by the @code{grep-save-buffers} variable.
 The possible values are either @code{nil} (don't save), @code{ask}
-(ask before saving), a function which will be used as a predicate (and
-is called with the file name as the parameter and should return
-non-nil if the buffer is to be saved), and any other non-@code{nil}
-value means that all buffers should be saved without asking.
+(ask before saving), or a function which will be used as a predicate
+(and is called with the file name as the parameter and should return
+non-@code{nil} if the buffer is to be saved).  Any other
+non-@code{nil} value means that all buffers should be saved without
+asking.
 
 @findex grep-find
 @findex find-grep

doc/emacs/frames.texi

@@ -243,9 +243,9 @@ location of point.  Double-clicking on the end of a parenthetical
 grouping or end string-delimiter keeps point at the end of the region
 by default, so the beginning of the region will not be visible if it
 is above the top of the window; setting the user option
-@code{mouse-select-region-move-to-beginning} to non-nil changes this
-to move point to the beginning of the region, scrolling the display
-backward if necessary.
+@code{mouse-select-region-move-to-beginning} to non-@code{nil} changes
+this to move point to the beginning of the region, scrolling the
+display backward if necessary.
 
 @item Double-Drag-mouse-1
 Select the text you drag across, in the form of whole words.
@@ -1094,18 +1094,6 @@ file on a Dired buffer moves or copies the file (according to the
 conventions of the application it came from) into the directory
 displayed in that buffer.
 
-@vindex mouse-drag-and-drop-region
-  Emacs can also optionally drag the region of text by mouse into
-another portion of this or another buffer.  To enable that, customize
-the variable @code{mouse-drag-and-drop-region} to a non-nil value.
-Normally, the text is moved, i.e. cut and pasted, when the destination
-is the same buffer as the origin; dropping the region on another
-buffer copies the text instead.  If the value of this variable names a
-modifier key, such as @samp{shift} or @samp{control} or @samp{alt},
-then pressing that modifier key when dropping the text will copy it
-instead of cutting it, even if you drop on the same buffer as the one
-from which the text came.
-
 @vindex dnd-open-file-other-window
   Dropping a file normally visits it in the window you drop it on.  If
 you prefer to visit the file in a new window in such cases, customize
@@ -1114,6 +1102,19 @@ the variable @code{dnd-open-file-other-window}.
   The XDND and Motif drag and drop protocols, and the old KDE 1.x
 protocol, are currently supported.
 
+@vindex mouse-drag-and-drop-region
+  Emacs can also optionally drag the region with the mouse into
+another portion of this or another buffer.  To enable that, customize
+the variable @code{mouse-drag-and-drop-region} to a non-@code{nil}
+value.  Normally, the text is moved, i.e. cut and pasted, when the
+destination is the same buffer as the origin; dropping the region on
+another buffer copies the text instead.  If the value of this variable
+names a modifier key, such as @samp{shift}, @samp{control} or
+@samp{alt}, then pressing that modifier key when dropping the text
+will copy it instead of cutting it, even if you drop on the same
+buffer as the one from which the text came.
+
+
 @node Menu Bars
 @section Menu Bars
 @cindex Menu Bar mode

doc/emacs/search.texi

@@ -1746,12 +1746,13 @@ prompt, you can reuse search strings from previous incremental
 searches.  The text that matched is highlighted using the @code{match}
 face.  A numeric argument @var{n} specifies that @var{n} lines of
 context are to be displayed before and after each matching line.
+
 The default number of context lines is specified by the variable
-@code{list-matching-lines-default-context-lines}.
-When @code{list-matching-lines-jump-to-current-line} is non-nil,
-the current line is shown highlighted with face
-@code{list-matching-lines-current-line-face} and the point is set
-at the first match after such line.
+@code{list-matching-lines-default-context-lines}.  When
+@code{list-matching-lines-jump-to-current-line} is non-@code{nil} the
+current line is shown highlighted with face
+@code{list-matching-lines-current-line-face} and the point is set at
+the first match after such line.
 
 You can also run @kbd{M-s o} when an incremental search is active;
 this uses the current search string.

doc/lispref/compile.texi

@@ -94,7 +94,7 @@ the @code{byte-compile} function.  You can compile a whole file with
 recorded in a buffer called @file{*Compile-Log*}, which uses
 Compilation mode.  @xref{Compilation Mode,,,emacs, The GNU Emacs
 Manual}.  However, if the variable @code{byte-compile-debug} is
-non-nil, error message will be signaled as Lisp errors instead
+non-@code{nil}, error messages will be signaled as Lisp errors instead
 (@pxref{Errors}).
 
 @cindex macro compilation

doc/lispref/files.texi

@@ -2284,7 +2284,8 @@ because this is not portable.  Always use
 @code{file-name-as-directory}.
 
   To avoid the issues mentioned above, or if the @var{dirname} value
-might be nil (for example, from an element of @code{load-path}), use:
+might be @code{nil} (for example, from an element of @code{load-path}),
+use:
 
 @example
 (expand-file-name @var{relfile} @var{dirname})

doc/lispref/functions.texi

@@ -1748,8 +1748,8 @@ code) obey the advice and other calls (from C code) do not.
 @defmac define-advice symbol (where lambda-list &optional name depth) &rest body
 This macro defines a piece of advice and adds it to the function named
 @var{symbol}.  The advice is an anonymous function if @var{name} is
-nil or a function named @code{symbol@@name}.  See @code{advice-add}
-for explanation of other arguments.
+@code{nil} or a function named @code{symbol@@name}.  See
+@code{advice-add} for explanation of other arguments.
 @end defmac
 
 @defun advice-add symbol where function &optional props

doc/lispref/keymaps.texi

@@ -988,8 +988,9 @@ function is called with no arguments, prior to running each command,
 while @var{keymap} is active; it should return non-@code{nil} if
 @var{keymap} should stay active.
 
-The optional argument @var{on-exit}, if non-nil, specifies a function
-that is called, with no arguments, after @var{keymap} is deactivated.
+The optional argument @var{on-exit}, if non-@code{nil}, specifies a
+function that is called, with no arguments, after @var{keymap} is
+deactivated.
 
 This function works by adding and removing @var{keymap} from the
 variable @code{overriding-terminal-local-map}, which takes precedence

doc/lispref/lists.texi

@@ -1514,9 +1514,10 @@ of property lists and association lists.
 @defun assoc key alist &optional testfn
 This function returns the first association for @var{key} in
 @var{alist}, comparing @var{key} against the alist elements using
-@var{testfn} if non-nil, or @code{equal} if nil (@pxref{Equality
-Predicates}).  It returns @code{nil} if no association in @var{alist}
-has a @sc{car} equal to @var{key}.  For example:
+@var{testfn} if it is non-@code{nil} and @code{equal} otherwise
+(@pxref{Equality Predicates}).  It returns @code{nil} if no
+association in @var{alist} has a @sc{car} equal to @var{key}.  For
+example:
 
 @smallexample
 (setq trees '((pine . cones) (oak . acorns) (maple . seeds)))

doc/lispref/windows.texi

@@ -3059,7 +3059,7 @@ This function handles @var{window} and its buffer after quitting.  The
 optional argument @var{window} must be a live window and defaults to
 the selected one. The function's behavior is determined by the four
 elements of the @code{quit-restore} window parameter (@pxref{Window
-Parameters}), which is set to nil afterwards.
+Parameters}), which is set to @code{nil} afterwards.
 
 The window is deleted entirely if: 1) the first element of the
 @code{quit-restore} parameter is one of 'window or 'frame, 2) the
@@ -3126,7 +3126,7 @@ possible to set it manually, using the following code for displaying
 @end group
 @end example
 
-Setting the window history to nil ensures that a future call to
+Setting the window history to @code{nil} ensures that a future call to
 @code{quit-window} can delete the window altogether.
 
 @end defun