[PATCH] Support case insensitive header searches for MSVCCompat

[Saleem Abdulrasool]

  One of the nice things about clang is that it is inherently a cross-compiler :-).  Not all file systems are case-insensitive, and unfortunately, as I mentioned in the commit message, the Windows SDK does get the case wrong in many cases.  This is an attempt to make the cross-compiler work properly with MS compatibility irrespective of the environment where it is being executed.

http://llvm-reviews.chandlerc.com/D2972