msx2: fix video

With these small vdp corrections we have a proper 80x25 display
vdp: scrolling sizes are wrong

Fix some hex/dec confusions
binman: minor cleaning/commenting
msx: Add initial (non working) bootrom test, also make it build fuzix.com
msx2: fix crash on outchar debug
msx1: Add the initial bits

This is basically in parallel with MSX2 but with the various memory manager
bits stripped out (new one needed) and 40 char vdp code
msx1: sketch out the bits needed to work the brain dead slot system

Plus find the megarams.

All untested.
README: Random ramblings about how a port might work
msx1: memory mapping and other logic

The big TODO for userspace here is to implement forkcopy (copying 32K between
two blocks of MegaRAM)