C65: implement "$D030.6 VIC-III:CROM9 Select between C64 and C65 charset"

[lgblgblgb]

Currently bit 6 of VIC-III register $D030 is not emulated. On C65 emulator is kinda straightforward to do. In case of the MEGA65 it's a bit more complicated because:

• it needs larger WOM, which affects the global memory map + decoding + charset loading/refresh, maybe time for the new memory decoding: MEGA65: introduce faster, shorter, more compatible, easy to maintain/understand/modify/follow memory and I/O decoding #209
• maybe for proper Hyppo level initialization it would need a more decent Hyppo, Xemu/MEGA65 is not ready for: MEGA65: adopt more decent hyppo #140
• VIC-IV rendering is more complex, also with Hernan's planned merge, too much things would change anyway: MEGA65: integrate Hernan's ideas/work on VIC-IV enhancements with the possibility of re-factoring meanwhile #29

This issue here is meant to be a reminder, so I won't forget the issue, also not the points above :)

[lgblgblgb]

Ok, wait a bit! (is it OK to talk to myself? ... ) According to Paul, even MEGA65 does not have this feature yet!

[lgblgblgb]

I think, this is a no-go for MEGA65 emulation as MEGA65 does not implement (??) this either. Must be checked for C65 emulation though.

[lgblgblgb]

MEGA65 has been excluded from this issue, as it seems even MEGA65 does not care (but C65 does, so it's a C65 specific issue from now on).