This caches the font list data to a file to minimize load times. Font
data will be refreshed when any font files are added/removed, based upon
a checksum of the font file names and dates (if available).
This uses fontconfig for looking up font files for freetype to use on
both linux and mac. It's apparently a bit more optimal and prevents us
from having to worry about the load time on the mac version as well.
Refactored and moved all the old code to the find-font-windows.c file,
as it's no longer used on anything but windows.