rgblink: Don't allocate unnecessary buffer. Delete unused flag.
rgbasm: Don't allocate an unnecessary buffer.
rgbasm: Fix TOCTOU and reduce buffering.
Unclutter Makefile: use $Q instead of ${Q}.
Wrap Makefile to 80 characters.
Improve POSIX compliance in the Makefile.

Set .POSIX and don't use the += operator.
rgbasm: Avoid unnecessary filename copying.
Remove dead stores.
Now that we replace missing libc functions, switch back to err().
Remove rgblib.

I have never used it and it's probably been broken for years.
Update license.
Fix MinGW target.
Revert 97d431d1f4ad404e282e3781bd195be3f053734d; it breaks things.
Separate errors that shouldn't have been combined in the first place.
Remove inconsistent version numbering.
Don't cast calls to malloc().
Fix dependencies for Yacc files. Improve Makefile POSIX compliance.

Parallel building issue pointed out by murphm8 and chastai.