Our points are more like fat lines than actual quads, in that they are scale-invariant.
All leaks found with valgrind while running the test suite. This commit also clears the Cairo cache to improve SNR of Valgrind output.
SurfaceRenderer is a new renderer implementing the Canvas interface running entirely on the CPU; it projects strokes and triangles in the exact same way as OpenGL would, and it can be used for rendering into raster or vector 2d surfaces.
