bug#21303: 25.0.50; incorrect doc string for `menu-set-font'

[Drew Adams <drew.adams@oracle.com>]

`C-h k' and choose `Set Default Font' from menu-bar menu `Options'.

The doc string says "Interactively select a font and make it the default
on all existing frames."

This is wrong.  The most important thing this command does is set the
font as the default for all FUTURE frames.  The doc string gives the
impression that it sets the default font only for the EXISTING frames.

Perhaps someone misread the doc string of `set-frame-font' when writing
the doc string of `menu-set-font', seeing only that arg FRAMES = t means
"all existing graphical frames".

The most important part of the behavior (and the doc string) of
`set-frame-font' is that a non-nil FRAME arg "alter[s] the user's
Customization settings as though the font-related attributes of the
`default' face had been "set in this session", so that the font is
applied to future frames."
^^^^^^^^^^^^^^^^^^^^^^^^

Users of `menu-set-font' should have this info, above all.


In GNU Emacs 25.0.50.1 (i686-pc-mingw32)
 of 2015-07-31 on LEG570
Bzr revision: 8d332aeccab2208e6c6bd434738565e6abf12043
Windowing system distributor `Microsoft Corp.', version 6.1.7601
Configured using:
 `configure --host=i686-pc-mingw32 --enable-checking=yes,glyphs'