dvisvgm needs rebuild to support ghostscript 10

[Martin Gieseking]

Hi,

besides the already mentioned issues with GS 10.0, the upcoming GS 10.1 
will completely break dvisvgm's PDF functionality because Artifex is 
finally going to remove the old PostScript-based PDF interpreter from 
GS. Unfortunately, the new C-based one doesn't allow for overriding PS 
operators which is required for dvisvgm to interact with the interpreter 
during the conversion process.

In order to keep the PDF functionality available, I've added an 
alternative PDF handler that uses mutool (part of mupdf) as a helper 
utility. As long as a GS version < 10.1 is present, the current 
mechanism is used, though. The new additions will be part of dvisvgm 3. 
It also comes with a newly implemented font writer module replacing the 
outdated, bundled FontForge library.

Regards,
Martin