Symbol parsing caps out at 32 characters

[fixermark]

If the size of a symbol exceeds the SBOLSZ - 1 limit (https://github.com/camsaul/nesasm/blob/master/source/symbol.c#L57), reading more characters for the symbol silently bails. This can cause aliasing of symbols if really_very_surprisingly_long_name and really_surprisingly_long_name_with_a_different_suffix are in the same program.

[camsaul]

Hey @fixermark, I don't have a ton of time to hunt down bugs like this myself but I'd be happy to merge a PR to fix it