[ms-inline asm] Remove the identifier parsing logic from the AsmParser.  This is
now taken care of by the frontend, which allows us to parse arbitrary C/C++
variables.
Part of rdar://13663589

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@180037 91177308-0d34-0410-b5e6-96231b3b80d8