Recommitting r358783 and r358786 "[MS] Emit S_HEAPALLOCSITE debug info" with...

Recommitting r358783 and r358786 "[MS] Emit S_HEAPALLOCSITE debug info" with fixes for buildbot error (undefined assembler label).

Summary:
This emits labels around heapallocsite calls and S_HEAPALLOCSITE debug
info in codeview. Currently only changes FastISel, so emitting labels still
needs to be implemented in SelectionDAG.

Reviewers: rnk

Subscribers: aprantl, hiraditya, cfe-commits, llvm-commits

Tags: #clang, #llvm

Differential Revision: https://reviews.llvm.org/D61083

llvm-svn: 359149