[ms-inline-asm] Implement align directive (which is roughly equivalent to .align).

Also, allow _EMIT and __EMIT for the emit directive.  We already do the same
for TYPE, SIZE, and LENGTH.
rdar://13200215


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@175008 91177308-0d34-0410-b5e6-96231b3b80d8