Reason: Self-modifying. -.-
Also, why no GRCG? Would have allowed blitting via REP MOVSD… Might as
well optimize all the way if you're going the ASM route to begin with.
Part of P0136, funded by [Anonymous].
Whew, time to look at every `int` variable we ever declared! The best
moment to do this would have been a year ago, but well, better late
than never. No need to communicate that in comments anymore.
These shouldn't be used for widths, heights, or sprite-space
coordinates. Maybe we'll cover that another time, this commit is
already large enough.
Part of P0111, funded by [Anonymous] and Blue Bolt.