Further simplify assembler parsing
Further simplify assembler parsing

The 'parse_label' function was replaced with a call to 'parse_ident' and a
little bit of processing; the original 'parse_label' was basically a copy of
'parse_ident' anyways.  As a bonus, this new version is marginally more
efficient.

ianprime0509/chip8,ianprime0509/chip8