Makefile: actually optimize build except for debug.
Bump version to 0.3.0.
Create CRC32 hash of rasterized line.

The bounding box alone is not enough information to determine whether
or not two lines are the same. Neither is a crc32 hash, but it's a far
sight better than just having the bounding box, and it's fast and easy.

By hashing the image color, bitmap and bounding box, a reasonably
unique hash can be created.
Update MSVS project.

Do not try to build with zlib on Windows.
C++ example: update to do things with hashes.
Aegisub example: add hash support.