[X86, inlineasm] Improve analysis of x,Y0,Yi,Ym,Yt,L,e,Z,s asm constraints (patch by Alexey Frolov)

Improve Sema checking of 9 existing inline asm constraints (‘x’, ‘Y*’, ‘L’, ‘e’, ‘Z’, ‘s’).
Differential Revision: http://reviews.llvm.org/D10536

llvm-svn: 242665