Make imenu-flush-cache into a function

* doc/emacs/programs.texi (Imenu): Remove documentation.

* lisp/imenu.el (imenu-flush-cache): Make into a function, since
this isn't supposed to be used interactively.

doc/emacs/programs.texi

@@ -280,11 +280,6 @@ changes in the text.
 than @code{imenu-auto-rescan-maxout} in bytes, and scanning is
 stopped if it takes more than @code{imenu-max-index-time} seconds.
 
-@findex imenu-flush-cache
-  You can force Imenu to forget the buffer's index with @w{@kbd{M-x
-imenu-flush-cache @key{RET}}}.  This causes Imenu to rescan the
-current buffer next time you invoke @kbd{M-g i} in that buffer.
-
 @vindex imenu-sort-function
   You can customize the way the menus are sorted by setting the
 variable @code{imenu-sort-function}.  By default, names are ordered as

etc/NEWS

@@ -666,7 +666,7 @@ available options can be restored by enabling this option.
 *** 'imenu' is now bound to 'M-g i' globally.
 
 ---
-*** New command 'imenu-flush-cache'.
+*** New function 'imenu-flush-cache'.
 Use it if you want Imenu to forget the buffer's index alist and
 recreate it anew next time 'imenu' is invoked.
 

lisp/imenu.el

@@ -903,9 +903,8 @@ for more information."
   "Flush the current imenu cache.
 This forces a full rescan of the buffer to recreate the index alist
 next time `imenu' is invoked."
-  (interactive)
-  (setq imenu--index-alist nil)
-  (message "Flushed the imenu cache"))
+  (imenu--cleanup)
+  (setq imenu--index-alist nil))
 
 (provide 'imenu)