Compile labels to short literals where possible

[Twisol]

This compiles to 7DC1 0002:

SET PC, loop
:loop

However, this compiles to 85C1:

SET PC, 1

They both do the same thing, but the latter uses one less word.

[mappum]

I know. I implemented the labels to always use another word. I've planned on fixing that, but since it doesn't affect functionality, it hasn't been the highest priority.

[Twisol]

Okay. I'm just adding things to the issue tracker as they come up.