Use custom assembly parser class for memory operands (instead of hard-coding in ParseInstruction)
- When looking for which operands need custom formatters, TableGen only considers the stem of the instruction.  Since masked instructions different in the number and types of parameters (and previously had the same stem mnemonic and dotted qualifiers), these would conflict.  I have altered the assembly language so I now use underscores where I previously used dots.
- Fixed a bug with where the offset of invalid assembly operands was not reported correctly
Simplify IntCompareInst form by removing extra opsign parameter and just combining into mnemonic
Remove custom directive .word, which is unnecessary since there is already a built in .long that does the same thing.