[PATCH] Enhance TTF/OTF support beyond Windows

Currently, cmap tables in TTF/OTF are only supported for Platform ID = 3, i.e. MS Windows. There is no support for Platform ID = 0, i.e. basic Unicode, or 1, i.e. Macintosh.

This makes quite some system fonts bundled with OS X supposedly unusable. The solution is fairly trivial (patch proposal will be attached shortly), provided the cmap table format in the font is already supported. FOP currently only has support for cmap format 4 (segment to delta mapping), but this seems to suffice for most of the Unicode cmaps as well.

See also FOP-2539, which triggered me to investigate this closer.