[PGO] Enable building compiler-rt profile support library on Windows

Summary: This change configures Windows builds to build the complier-rt profile support library (clang_rt.profile-i386.lib). Windows API incompatibilities in the compiler-rt profile lib are also fixed.

Reviewers: davidxl, dnovillo

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D15830

llvm-svn: 256848