Declare templabelcount as a global in atom().
Add missing 'sys.' and remove unused module import.
Exit with exit code 1 if there were errors, 0 otherwise.
Merge pull request #17 from catseye/exit-code-1-on-error

Exit with exit code 1 when errors occurred
Merge pull request #14 from catseye/fix-templabelcount

Declare templabelcount as a global in atom().
Second attempt at implementation of the BBXn instructions for Rockwell 65c02 chips.

Reliable technical documentation for how these instructions are decoded is a
little thin on the ground online, so some of this implementation is still
speculative.