Add 64-bit data support for memory commands

Add 64-bit data for memory commands, such as md, mw, mm, cmp. The new
size ".q " is introduced.

For 64-bit architecture, 64-bit data is enabled by default, by detecting
compiler __LP64__. It is optional for other architectures.

Signed-off-by: York Sun <yorksun@freescale.com>