- CRTC write: only the changes of the start address, the cursor position or   cursor size issue a screen update request - reading an invalid CRTC register returns 0 / writing is ignored - bit 7 of CRTC address register is always 0 - debug messages for CRTC registers updated / panics removed - use the number of visible columns in text mode when calculating the screen   width and the cursor position
- CRTC write: only the changes of the start address, the cursor position or
  cursor size issue a screen update request
- reading an invalid CRTC register returns 0 / writing is ignored
- bit 7 of CRTC address register is always 0
- debug messages for CRTC registers updated / panics removed
- use the number of visible columns in text mode when calculating the screen
  width and the cursor position

marmolejo/bochs-zet,marmolejo/bochs-zet,marmolejo/bochs-zet,marmolejo/bochs-zet,marmolejo/bochs-zet