Use predefined constants when possible

Now we can assume that D2D1_DRAW_TEXT_OPTIONS_ENABLE_COLOR_FONT is always defined in the Windows SDK.  Hence we don't need to have our own definition anymore.

This CL is just a removal of redundant code.  No behavior change is intended.

BUG=none
TEST=none

git-svn-id: https://mozc.googlecode.com/svn/trunk@538 a6090854-d499-a067-5803-1114d4e51264