bug#19593: 25.0.50; REGRESSION: `underline' face property lost color possibility

[Drew Adams]

At least in the Customize UI, you can no longer define the color of
an underline.

The regression was apparently introduced in Emacs 24.3.  It presumably
was not done deliberately, as it is an incompatible change and I do not
find it mentioned in NEWS.

Attribute `overline' still has a color possibility, but not `underline'.
At least not in the Customize UI.


In GNU Emacs 25.0.50.1 (i686-pc-mingw32)
 of 2014-10-20 on LEG570
Bzr revision: 118168 rgm@gnu.org-20141020195941-icp42t8ttcnud09g
Windowing system distributor `Microsoft Corp.', version 6.1.7601
Configured using:
 `configure --enable-checking=yes,glyphs CPPFLAGS=-DGLYPH_DEBUG=1'