Less memory-hungry MPEG playback
This is an attempt to adapt some code from SDL to make the MPEG cutscene player less memory hungry.
With our current code, we allocate a lookup table of 256 * (BITDEPTH + 1)^2 OverlayColor entries. I believe this comes out to about 8 MB of data; data that is shared between all instances of the cutscene player, so it's not freed between cutscenes. With the new code, two lookup tables are allocated. One that's 4 KB (assuming an int is four bytes) and one that's 9 KB.
I haven't touched the 8-bit case, but I think the lookup table for that one is around 70 KB so it's not too bad.
Note that this is still fairly untested code. There could be out-of-bounds memory access, and I haven't had much time to compare the output or the performance to the current version yet. And I've probably only tried the 555 case, not the 565 case. So if anyone else wants to try it, I'd be grateful.
Ticket imported from: #1155731. Ticket imported from: patches/506.