Mac OS X Background Color Bug Fix

[Andrew Choi]

Hi,

Just checked in a bug fix that corrects a problem with Emacs on Mac OS
X not properly using the background color set in default-frame-alist.

If the background color you set only shows for areas with text and a
white background is displayed for areas without text, this patch
should be the solution.

This fix was sent by Steven Tamm.  Amos at UT Dallas helped test it.

Thank you both!

Andrew.