[ms-inline asm] Pass a StringRef reference to ParseIntelVarWithQualifier so we
can build up the identifier string.  No test case as support for looking up
these type of identifiers hasn't been implemented on the clang side.
Part of rdar://13499009
Aliasing rules for struct-path aware TBAA.

Added PathAliases to check if two struct-path tags can alias.
Added command line option -struct-path-tbaa.