ACIA driver

Manage I/O from an asynchronous communication interface adapter
(ACIA). provides "EMIT" to put c char on the ACIA as well as
an input buffer. You have to call "~ACIA" on interrupt for
this module to work well.

CONFIGURATION

ACIA_CTL: IO port for the ACIA's control registers
ACIA_IO: IO port for the ACIA's data registers
ACIA_MEM: Address in memory that can be used variables shared
          with ACIA's native words. 8 bytes used.

Load z80 words with "352 LOAD" and Forth words with "357 LOAD".