- switch M00 to AXI3
- remove a lot of unnecessary static register inits
- centralize Z3 data strobe flags
- react quicker to FCS, address, r/w and strobes to fix A4000/CyberStorm
- make dtack timeout controllable and default to 3 cycles
- pipeline some registers
- unify Denise(A500) and Videoslot capture
- one-hot encode videocap state machine
- decouple z_reset from zorro_state case

VARIANT_FW20 is for firmware 2.0 development work.

Video capture needs some tweaks to letterboxing/cropping.

Only renders each pattern row once if the drawing mode is JAM2 and no mask is needed, then copies the lines that have already been rendered instead of processing them again.

CAUTION: verified only on A4000D + A3660
bustest results (bustest ADDR=40100000 MEGA):
 Read: 6.3 MB/s
Write: 8.0 MB/s

Rename ZZ9000Test -> ZZ9000OS in documentation

This was renamed in the source tree a while ago,
adjust documentation.

Hide hardware sprite if video capture (scandoubler) is enabled, show hardware sprite if it is currently disabled.