Mark intrinsic functions as llvm-specific.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@212347 91177308-0d34-0410-b5e6-96231b3b80d8
Avoid mangling names twice. No functionality change.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@212348 91177308-0d34-0410-b5e6-96231b3b80d8