Add profiling support for Intel Parallel Amplifier XE (VTune) for JITted code in LLVM.

Also refactor the existing OProfile profiling code to reuse the same interfaces with the VTune profiling code.
In addition, unit tests for the profiling interfaces were added.

This patch was prepared by Andrew Kaylor and Daniel Malea, and reviewed in the llvm-commits list by Jim Grosbach

llvm-svn: 152620