Moved the BT48x hardware cursor draw function to the RAMDAC's code where it belongs;
Renamed the BT48x RAMDAC code file to vid_bt48x_ramdac.c (was vid_bt485_ramdac.c);
Fixed BT48x 64x64 hardware cursor bugs (caused by the index variable being uint8_t when it should have been uint16_t) introduced in the previous commit.
IBM.H is gone, video stuff re-organized. Keyboard stuff reorganized.
Machines that have their own video, mouse and/or keyboard now have all this in their machine file.
Fixed and other cleanups here and there.
