This updates most pre-32bit systems to have hardware accurate borders and
aspect ratio where known, reasonable estimates are used where not known.
This also means that PAL games will use the correct PAL aspect rather than
using the NTSC pixel aspect ratio.
All TMS9918 VDP based consoles are thought to be be correct, as are Master
System, Mega Drive, and NES, while SNES and PC-Engine are (educated)
estimates.
The overscan option has been reworked to crop all non-desirable edges of the
screen, including borders and areas that often contain garbage data, previously
this option only cropped the bottom 16 lines of active display.
The reworked overscan is not yet implemented for Atari 2600, PC-Engine, N64 or
PlayStation.
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