bug#15748: 24.3.50; `customize-group': Provide a way to hide/show all values

[Drew Adams]

This bug was introduced in Emacs 24 (in Emacs 23, at least some
values were shown by default).

To see all option values, a user must now click *each*
`Show Value' link.  Likewise, to hide all, a user must click
*each* `Hide' link.

Please provide buttons to `Show All Values' and `Hide All Values'.
And please add such items to the `Custom' menu-bar menu.


In GNU Emacs 24.3.50.1 (i686-pc-mingw32)
 of 2013-10-19 on LEG570
Bzr revision: 114715 rgm@gnu.org-20131019023520-s8mwtib7xcx9e05w
Windowing system distributor `Microsoft Corp.', version 6.1.7601
Configured using:
 `configure --enable-checking 'CFLAGS=-O0 -g3' CPPFLAGS=-DGLYPH_DEBUG=1'