Driver: Accept -fprofile-instr-use and -fprofile-instr-generate

These flags will be used for instrumentation based PGO.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@198639 91177308-0d34-0410-b5e6-96231b3b80d8
CodeGen: Initial instrumentation based PGO implementation

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@198640 91177308-0d34-0410-b5e6-96231b3b80d8