The fontconfig collector should now always pick the exact font files
used by libass rather than a giant mishmash of vaguely related files
which may or may not include the correct font.
Make the freetype font collector windows-only, as it's far inferior to
the fontconfig collector and is only present as a fallback.
Add option to copy the fonts to the script's folder.
Closes#1059.
Originally committed to SVN as r6279.