TRS-80 Recipe

Support code for the TRS-80 recipe. Contains drivers for the
keyboard, video and floppy. At the moment, they are thin layer
over the drivers provided by TRSDOS' SVC.

Load the Z80 words with "492 LOAD" and the high level part
with "498 LOAD".

There is also the RECV program at B502 and the XCOMP unit at
B504