Add MOVSX[D] -> CBW/CWDE/CDQE optimization patterns when the suitable
form of the AX register are referenced.
Add MOVZX reg64,rm32 pattern which converts to a 32-bit MOV.
Add MOVZXD reg64,rm32 alias pattern for consistency.
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
