This somewhat reverts 2b9f130 , while keeping tidier code and safer args.
Switching from lzwexpand_to_mem to using streams only caused speed
regression, which became notable for hi-res games with LZW sprite
compression (a 3.6.0 feature).
For this revert we instead load compressed data into a buffer in whole,
then pass two memory buffer pointers to lzw_expand, where it reads
and writes memory directly.
Testing a high-res (1920x1080) game with lots of sprite streaming
showed speed improvement of this function by around 200%.
The downside is the temporary buffer for reading compressed
data too.
In theory, same could be done for lzwcompress afterwards.
From upstream 6959004676916568c6fca210702d669f61741e13
D G Turner
Walter Agazzi
Paul Gilbert
Eugene Sandulenko