`pcx2clx` width cropping support

#7

Re-encode CL2

Original Blizzard encoder is slightly less optimal than our encoder, so we now re-encode the graphics of CL2 files as well.

Savings for unpacked and minified MPQs:

• diabdat.mpq: 918,311 bytes.
• hellfire.mpq: 313,882 bytes.

Example player graphics (note that only a few are loaded at any given time for single player):

• diabdat/plrgfx/warrior/: 366,564 bytes.

Example monster graphics:

• diabdat/monsters/skelbow: 5,391 bytes.

Initial release

This initial release provides 4 binaries for converting to/from CLX, a custom graphics format used by DevilutionX.

The CLX format is nearly identical to the original Diablo's CL2.
The only difference is that CLX specifies frame width and height in the frame header.

These binaries can convert in the following directions:

• CEL, CL2, PCX → CLX
• CLX → PCX

Known issue: the Windows binaries only support ASCII paths.