bug#40375: 27.0.50; yank unexpectedly depends on progn

[Noam Postavsky]

Markus Triska <triska@metalevel.at> writes:

> Please consider documenting this in the description of `yank'. Other
> than that, I consider this issue resolved.

Does this look okay?  (modulo a fill-paragraph which I've held off on
just to make the patch easier to read)

--- i/lisp/simple.el
+++ w/lisp/simple.el
@@ -5110,7 +5110,9 @@ yank-pop
 (defun yank (&optional arg)
   "Reinsert (\"paste\") the last stretch of killed text.
 More precisely, reinsert the most recent kill, which is the
-stretch of killed text most recently killed OR yanked.  Put point
+stretch of text most recently killed or yanked.  Or text from the
+system clipboard if that was modified more recently (see
+`interprogram-paste-function').  Put point
 at the end, and set mark at the beginning without activating it.
 With just \\[universal-argument] as argument, put point at beginning, and mark 
at end.
 With argument N, reinsert the Nth most recent kill.