Add a new flag, -fms-inline-asm, that enables the output of MS-style inline

assembly.  

By default, we don't emit IR for MS-style inline assembly (see r158833 as to 
why).  This is strictly for testing purposes and should not be enabled with the
expectation that things will work.  This is a temporary flag and will be removed
once MS-style inline assembly is fully supported.

llvm-svn: 160573