numbers: parse tasm-style numbers with prefixes and suffixes
use 'equ' instead of '=' for tasm compatibility
implement DW pseudo-instruction
spell ORG like tasm
temporarily(?) make range messages into warnings
fix comment stripping

the sequence
 stab YH ; comment
didn't parse because of trailing space
Always match first instruction from table

.. this requires explicitly matching the space after an instruction
because otherwise the pattern order
 JMP *
 JMPNZ *
would cause 'JMPNZ LABEL' to actually parse as 'JMP NZ LABEL', and
issue an error due to the trailing 'LABEL'.  (This doesn't actually
make sense to me, except that it's what pyparsing seemed to do)