Trac #21647

This allows ANGLE to be built with either the Win8 SDK or the DX SDK
with appropriate configuration on a VS2010 install.  See wiki for details.

Signed-off-by: Shannon Woods
Signed-off-by: Nicolas Capens

git-svn-id: https://angleproject.googlecode.com/svn/trunk@1315 736b8ea6-26fd-11df-bfd4-992fa37f6226