InstrProf: Use LLVM's -instrprof pass for profiling

The logic for lowering profiling counters has been moved to an LLVM
pass. Emit the intrinsics rather than duplicating the whole pass in
clang.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@223683 91177308-0d34-0410-b5e6-96231b3b80d8