Updates for DHGR MIX (#633):
. Support new switch -rgb-card-invert-bit7 to invert bit7 for Dragon Wars.
- Reverted DHGR MIX mode and AN2 off to invert bit7
. Support DHGR MIX mode and AN2 off to invert bit7 (undocumented)
. Improve the video-mode precondition to check for 80COL access occurring before $C05F
Supported modes selected via toggling AN3 and clocking in 80COL:
- 140 color mode (Apple calls this mode 2, Video7 calls this mode 0).
- mixed mode (Apple calls this mode 3, Video7 calls this mode 2).
- 560 mono mode (Apple calls this mode 1, Video7 calls this mode 3).
Save-state is also persists the extra state.
And there's a few corrections to APPLE2E.SYM for the 80STORE and 80COL I/O addresses.