Truetype fonts, Unicode support, and arc drawing improvements.

Hey Tony,

I've done some more work on the Unicode support and text selection works again (but only on Adobe Reader). We've also made some patches to the TrueType font handling so that more fonts can be used, and font loading is more modular (it is possible to load the same font twice -- the second time is simply ignored).

Because I get many emails of people that are not managing to apply the unicode patch to libharu, I've temporarily created this git tree. I hope you can review and pull the changes into your tree soon.

Regards,
koen