[AC21.5] Cleaning out old work #6: Make auto-save-timeout customizable

APPROVE COMMIT 21.5

"Obviously correct", to coin a phrase.

diff -r ba779e0bbd09 -r 9d87c0e5505b lisp/ChangeLog
--- a/lisp/ChangeLog	Mon Jan 04 15:33:19 2016 +0900
+++ b/lisp/ChangeLog	Mon Jan 04 16:07:12 2016 +0900
@@ -3,6 +3,10 @@
 	* info.el (Info-read-subfile): Follow change in Makeinfo 5.0 with
 	arithmetic of node positions.
 
+2015-06-22  Stephen J. Turnbull  <[email protected]>
+
+	* itimer-autosave.el (auto-save-timeout): Customize in group 'auto-save.
+
 2015-06-11  Aidan Kehoe  <[email protected]>
 
 	* cl-macs.el (equalp):
diff -r ba779e0bbd09 -r 9d87c0e5505b lisp/itimer-autosave.el
--- a/lisp/itimer-autosave.el	Mon Jan 04 15:33:19 2016 +0900
+++ b/lisp/itimer-autosave.el	Mon Jan 04 16:07:12 2016 +0900
@@ -31,7 +31,7 @@
 ;;; Code:
 
 ;jwz: this is preloaded so don't ;;;###autoload
-(defvar auto-save-timeout 960
+(defcustom auto-save-timeout 960
   "*Number of seconds idle time before auto-save.
 Zero or nil means disable auto-saving due to idleness.
 
@@ -42,7 +42,9 @@
 1000k buffer, and 4 1/2 times this in a 2000k buffer.
 
 See also the variable `auto-save-interval', which controls auto-saving based
-on the number of characters typed.")
+on the number of characters typed."
+:type 'integer
+:group 'auto-save)
 
 ;jwz: this is preloaded so don't ;;;###autoload
 (defvar auto-gc-threshold (/ gc-cons-threshold 3)