Updating print/mupdf to mupdf-1.3

Hello to the entire pkgsrc community!
I have just added to pkgsrc-wip wip/mupdf (1.3) intended to replace
print/mupdf (1.1).
I avoided to directly send a PR because it still need testing, cleanups
and improvements.

For more information of what should be done before importing please give
a look to TODO.
I've also documented everything that could be useful to understand the
changes that I did there.


Thank you very much in advance,
L.