[hatari-devel] TT palette bankswitching should be supported

["Roger Burrows" <anodyne@xxxxxxxxxxxx>]

When running in ST Low, ST medium, or TT medium, the TT video hardware supports 
bankswitching for the palette: the part of the TT palette that maps to the 
STe-compaitble palette can be changed, by changing the "bank number" in the TT 
shifter.

After power-on reset, the bank number is the set to zero, which causes the 
first 16 TT palette registers to map to the STe palette registers.  If you set 
the bank number to N, then TT palette registers 16*N to 16*N+15 are mapped 
instead.  There is even a special TOS3 XBIOS call, EsetBank(), to do this.

Hatari does not support this.  

In video.c, function Video_TTShiftMode_WriteWord(), I think that there needs to 
be a check for bank number, which would then be used (I don't want to guess 
where) to do the mapping.

Tested on a real TT, and documented in "Atari TT030 Hardware Reference Manual".

Roger