[ms-inline asm] Add support in the X86AsmPrinter for printing memory references

in the Intel syntax.

The MC layer supports emitting in the Intel syntax, but this would require the
inline assembly MachineInstr to be lowered to an MCInst before emission.  This
is potential future work, but for now emitting directly from the MachineInstr
suffices.

llvm-svn: 165173