Updated perf support.
Generate a binary-encoded profile for LLVM profiles. This changes the LLVM profile writer to use a more compact binary encoding, as supported in upstream LLVM as of http://llvm.org/viewvc/llvm-project?rev=250539&view=rev This change breaks compatibility with previous versions. To dump the generated file, you will need to use the llvm-profdata tool in LLVM. Make sure to get a version of llvm-profdata at at least revision 250539.