[Coco] mess HD problem

[Robert Gault]

When using 2 .vhd drives on an emulator where the drives need to be read under 
the Disk Basic ROM, you will need a modified ROM. If these drives are only to be 
used under NitrOS-9, the solution is much easier.

Sourceforge contains in 3rdparty a version of emudsk for MESS that will handle 2 
.vhd drives. You will need to assemble that code.

For the JVC Coco3 emulator, just take your current emudsk (for a single .vhd 
drive) and /h0, copy them to emudsk2 and /h1, use dEd to change all $FF8x to 
$FFEx in emudsk2, and change the length of the descriptor and name in h1 from H0 
to H1 and EmuDsk to EmuDsk2.
No recompilation will be necessary. The length of emudsk2 will be so short that 
the increase in os9boot would be negligible but you don't really need to change 
os9boot. You can load the merged emudsk2 and h1 from the startup file or as 
needed to read the second .vhd.

Robert