Copy-edit doc strings and comments wrt bignum and fixnum

Don't say that a value is a fixnum if small enough and a bignum
otherwise, because that is now how Lisp integers always work,
and we generally don't expose the fixnum/bignum difference to the user
unless really necessary.

* src/charset.c (Fencode_char):
* src/editfns.c (Fuser_uid, Fuser_real_uid, Fgroup_gid)
(Fgroup_real_gid, Femacs_pid):
* src/font.c (Ffont_variation_glyphs):
* src/process.c (Fprocess_id):
Edit doc strings.
* src/pgtkselect.c:
* src/xselect.c: Edit comments.

src/charset.c

@@ -1852,9 +1852,8 @@ although this usage is obsolescent.  */)
 
 DEFUN ("encode-char", Fencode_char, Sencode_char, 2, 2, 0,
        doc: /* Encode the character CH into a code-point of CHARSET.
-Return the encoded code-point, a fixnum if its value is small enough,
-otherwise a bignum.
-Return nil if CHARSET doesn't support CH.  */)
+Return the encoded code-point as an integer,
+or nil if CHARSET doesn't support CH.  */)
   (Lisp_Object ch, Lisp_Object charset)
 {
   int c, id;

src/editfns.c

@@ -1172,8 +1172,7 @@ This ignores the environment variables LOGNAME and USER, so it differs from
 }
 
 DEFUN ("user-uid", Fuser_uid, Suser_uid, 0, 0, 0,
-       doc: /* Return the effective uid of Emacs.
-Value is a fixnum, if it's small enough, otherwise a bignum.  */)
+       doc: /* Return the effective uid of Emacs, as an integer.  */)
   (void)
 {
   uid_t euid = geteuid ();
@@ -1181,8 +1180,7 @@ Value is a fixnum, if it's small enough, otherwise a bignum.  */)
 }
 
 DEFUN ("user-real-uid", Fuser_real_uid, Suser_real_uid, 0, 0, 0,
-       doc: /* Return the real uid of Emacs.
-Value is a fixnum, if it's small enough, otherwise a bignum.  */)
+       doc: /* Return the real uid of Emacs, as an integer.  */)
   (void)
 {
   uid_t uid = getuid ();
@@ -1208,8 +1206,7 @@ Return nil if a group with such GID does not exists or is not known.  */)
 }
 
 DEFUN ("group-gid", Fgroup_gid, Sgroup_gid, 0, 0, 0,
-       doc: /* Return the effective gid of Emacs.
-Value is a fixnum, if it's small enough, otherwise a bignum.  */)
+       doc: /* Return the effective gid of Emacs, as an integer.  */)
   (void)
 {
   gid_t egid = getegid ();
@@ -1217,8 +1214,7 @@ Value is a fixnum, if it's small enough, otherwise a bignum.  */)
 }
 
 DEFUN ("group-real-gid", Fgroup_real_gid, Sgroup_real_gid, 0, 0, 0,
-       doc: /* Return the real gid of Emacs.
-Value is a fixnum, if it's small enough, otherwise a bignum.  */)
+       doc: /* Return the real gid of Emacs, as an integer.  */)
   (void)
 {
   gid_t gid = getgid ();
@@ -1306,8 +1302,7 @@ DEFUN ("system-name", Fsystem_name, Ssystem_name, 0, 0, 0,
 }
 
 DEFUN ("emacs-pid", Femacs_pid, Semacs_pid, 0, 0, 0,
-       doc: /* Return the process ID of Emacs, as a number.
-Value is a fixnum, if it's small enough, otherwise a bignum.  */)
+       doc: /* Return the process ID of Emacs, as an integer.  */)
   (void)
 {
   pid_t pid = getpid ();

src/font.c

@@ -4691,8 +4691,7 @@ Each element of the value is a cons (VARIATION-SELECTOR . GLYPH-ID),
 where
   VARIATION-SELECTOR is a character code of variation selector
     (#xFE00..#xFE0F or #xE0100..#xE01EF).
-  GLYPH-ID is a glyph code of the corresponding variation glyph,
-a fixnum, if it's small enough, otherwise a bignum.  */)
+  GLYPH-ID is a glyph code of the corresponding variation glyph, an integer.  */)
   (Lisp_Object font_object, Lisp_Object character)
 {
   unsigned variations[256];
@@ -4729,8 +4728,7 @@ a fixnum, if it's small enough, otherwise a bignum.  */)
    that apply to POSITION.  POSITION may be nil, in which case,
    FONT-SPEC is the font for displaying the character CH with the
    default face.  GLYPH-CODE is the glyph code in the font to use for
-   the character, it is a fixnum, if it is small enough, otherwise a
-   bignum.
+   the character, as an integer.
 
    For a text terminal, return a nonnegative integer glyph code for
    the character, or a negative integer if the character is not

src/pgtkselect.c

@@ -1248,8 +1248,7 @@ pgtk_get_window_property_as_lisp_data (struct pgtk_display_info *dpyinfo,
 	ATOM	32	> 1		Vector of Symbols
 	*	16	1		Integer
 	*	16	> 1		Vector of Integers
-	*	32	1		if small enough: fixnum
-					otherwise: bignum
+	*	32	1		Integer
 	*	32	> 1		Vector of the above
 
    When converting an object to C, it may be of the form (SYMBOL

src/process.c

@@ -1209,8 +1209,8 @@ If PROCESS has not yet exited or died, return 0.  */)
 
 DEFUN ("process-id", Fprocess_id, Sprocess_id, 1, 1, 0,
        doc: /* Return the process id of PROCESS.
-This is the pid of the external process which PROCESS uses or talks to.
-It is a fixnum if the value is small enough, otherwise a bignum.
+This is the pid of the external process which PROCESS uses or talks to,
+an integer.
 For a network, serial, and pipe connections, this value is nil.  */)
   (register Lisp_Object process)
 {

src/xselect.c

@@ -1754,8 +1754,7 @@ x_get_window_property_as_lisp_data (struct x_display_info *dpyinfo,
 	ATOM	32	> 1		Vector of Symbols
 	*	16	1		Integer
 	*	16	> 1		Vector of Integers
-	*	32	1		if small enough: fixnum
-					otherwise: bignum
+	*	32	1		Integer
 	*	32	> 1		Vector of the above
 
    When converting an object to C, it may be of the form (SYMBOL . <data>)