- for sequencer reg #1 a screen update is required after changing bit #0, #3 and #5
- added new method skip_update() that checks the conditions to skip the screen update
and it is called after resizing the display
- clear screen request from the sequencer is now handled by the update() code
in the new method skip_update() instead of clearing display directly
- added new class bx_vgacore_c containing the core of the standard VGA
emulation. This is now the base class for both vga and cirrus.
- created 2 separate plugins 'vga' (for standard VGA and VBE) and 'svga_cirrus'
(Cirrus emulation). The vga extension option is used to select which plugin
should be loaded.
- TODO: move the pcivga code to the VGA/VBE code, add subdirectory for display
adapters, severak improvements and cleanups
