Support compression algorithms

[velipso]

Would be nice to do something like:

.script
  i8 pack.huff pack.lz77 {1, 2, 3, 4, 5}
.end

and also:

.pack huff
  .pack lz77
    .i8 1, 2, 3, 4
    .embed 'file.bin'
  .end
.end

BIOS compression algorithms, according to GBATEK:

• BitUnPack bit
• Diff8bitUnFilter diff
• HuffUnComp huff
• LZ77UnComp lz77
• RLUnComp rle

Also, maybe a best option, which would try all of them, and pick whichever is smallest -- decompression works via checking the header.

see: https://github.com/devkitPro/grit/tree/master/libgrit