- Improve XMODEM reliability
- Convert rc2014/ps2 firmware ASM to Collapse OS ASM
- Make AVR PS/2 firmware a bit more Forth-friendly by reducing
  forward references (which are inherited from the old ASM code)
- Make AVR forward labels clearer. This scheme where FLBL only
  marks only to decide the jump type only later is really
  confusing. There has to be a better way.
- Make AVR asm endian-independant.