Touches a lot of code to remove long constants like "1L", so this patch is
large and ugly, but I think it makes all those Clamp() calls look nicer in
the long run.
Most of the game is 64-bit clean, since we can build without assembly code
now. I've marked the things that are obviously still wrong with STUBBED lines.
That being said: a 64-bit build can already run the demos mostly correctly,
so we're actually almost there!
There are a few obvious things that are obviously wrong, to be fixed.
