Drawing fat lines is slow on linux due to X11 having no direct
support for it. This leads to creating the PolyPolygon geometry
for each fat line, then tesselate and draw as trapezoids. This
is not buffered in any way and is done at each paint.
As a side effect, fat lines composed of multiple anti-aliased
lines also show errors since AA-ed edges do not add up graphically.
Since we have cairo now available it makes sense to use it
for fat line drawing, it is markedly faster despite being a software
renderer. No such gains for PolyPolygons though.

Change-Id: If4001556e2dd4c15ecf2587cad6ce1e864558f2d