RAM access via JTAG may interfere with CPU about vector06cc HOT 2 CLOSED

USB API is evil.

So far I could make it set HOLD signal upon iRxD_Ready, this way it manages to 
get
HLDA before actual RAM request needs completion. There's no flow control of any 
sort
so it's hard to interfere.. It works now, transparently, but it's far from 
being elegant.

Probably, it is possible to improve on it. In CMD_Decode, if oHOLD is set upon
RxD_Ready, iHLDA sets in time. The only problem, it seems, is that there are
different sorts of commands coming from Control Panel and they seem to lock this
simplistic circuit. 

Setting hold upon iRxD_Ready chronically doesn't work.. Having really no desire 
to
struggle with mostly a PC-side software issue (poorly written "Control Panel" 
demo),
this should pass for a fix.

 * Read/write of SRAM via USB API Control Panel works flawlessly.
 * Just for a case, manual bus hold switch added: SW7