[X86][MS-compatability][clang] allow MS TYPE/SIZE/LENGTH operators as a part...

[X86][MS-compatability][clang] allow MS TYPE/SIZE/LENGTH operators as a part of a compound expression

This patch introduces X86AsmParser with the ability to handle the aforementioned ops within compound "MS" arithmetical expressions.
Currently - only supported as a stand alone Operand, e.g.:
"TYPE X"
now allowed :
"4 + TYPE X * 128"

LLVM side: https://reviews.llvm.org/D31173
Differential Revision: https://reviews.llvm.org/D31174

llvm-svn: 298426