[PythonCAD] More Cairo drawing changes available at repo

[Art Haas]

Hi.

I've changed the code that draws the various Dimension entities to use
Cairo routines if they are available. The changes are now at the repo
and available to Subversion users via 'svn update'.

Art
-- 
Man once surrendering his reason, has no remaining guard against absurdities
the most monstrous, and like a ship without rudder, is the sport of every wind.

-Thomas Jefferson to James Smith, 1822