Hello!

The following updates Inkscape to its 1.0 version.  The test suite is
enabled and an effort is made to unbundle as much of 3rd party libraries
as possible (but more can be done, if you'd like to help: see the
comments in the patch).

The last patch of the series (Add libdepixelize) is added as a WIP, and
is included as a curiosity only (not intended to be merged in its
current state).

Enjoy!

Maxim