Some bad distributions (Debian) apparently are not good enough to
have a Pillow version from this decade packaged.
Therefore, we need to do it the painful way of prefixing our
symbols and refactoring everything to use them.
A new header file called "utils.h" has been added for this purpose,
and it is included in "overviewer.h".
The following macros have been prefixed with "OV_":
- MIN
- MAX
- CLAMP
- BLEND
- MULDIV255
Additionally, the C extension version was bumped to 56 because 55
was reverted back to 54.
Added resize_half() and resize_half_wrap() functions to composite.c and
overviewer.h, to replace the call to PIL's resize function made by
tileset.py. Also added "resize_half" to COverviewerMethods in main.c, so
it can be called from Python. Should increase performance by 10 to 20%
for the entire program.
closes issue #708
Props to mkor for taking advantage of the existing average loop, and
CounterPillow for sussing out the correct biome multiplication
color. This commit is just a teensy bit more future-proof.
