[PATCH] cpp11-migrate: Add a class to support include directives modifications (Windows bot fix)

[Edwin Vane]

  Not sure if this will work without you trying it first. It was a while back and perhaps there are better ways of doing it but I fixed these OS-specific file path problems in a way shown in the unittest Transform.isFileModifiable().

http://llvm-reviews.chandlerc.com/D1438