[cairo] libpixman API renames completed

[Dave Beckett]

I've completed the next stage of merging libpixregion and libic,
renaming the functions, types, enums to have a prefix of pixman or
PIXMAN (enum values).

The CVS (not in the pixman tarball) also contains a perl script
update.pl that can be used to update sources with the API changes.
Since I used it on the sources themselves to do the merge, I'm pretty
confident it works and is complete.

That finishes my work on the libpixman merge.  There are of course,
other cleanups and fixes now possible - so, go ahead!

Of course now cairo itself can be changed to use it.

Dave