CodeGen: Use a binary format for instrumentation based profiling

This updates CodeGenPGO to use the ProfileDataReader introduced to
llvm in r203703 and the new API for writing out the profile introduced
to compiler-rt in r203710.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@203711 91177308-0d34-0410-b5e6-96231b3b80d8