GAS has no such directives (not even mingw-w64 GAS has them), so I took
creative license with their names in assembly. I prefixed them all with
"w64_" to avoid namespace collisions, for example. If I discover that GAS
has taken a different approach, I'll change ours to match.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@131525 91177308-0d34-0410-b5e6-96231b3b80d8