Add support for disabling precompiled headers for source files of a different type than the source file that generated the PCH.
Add support for disabling precompiled headers for source files of a different
type than the source file that generated the PCH.

For now, this is VS 2010 only.
Review URL: http://codereview.chromium.org/7779050
witwall/gyp,witwall/gyp,witwall/gyp,witwall/gyp,witwall/gyp