[cairo-spans] Hook up filling paths with spans to cairo-surface-fallback.c.

This speeds up the mask generation step in cairo_fill() for the image
surface by up to 10x in especially favourable cases.

image-rgba                              twin-800 7757.80 0.20% -> 749.41 0.29%: 10.36x speedup
image-rgba spiral-diag-pixalign-nonzero-fill-512   15.16 0.44% ->   3.45 8.80%:  5.54x speedup

More typical simple non-rectilinear geometries are sped up by 30-50%.
This patch does not affect any stroking operations or any fill
operations of pixel aligned rectilinear geometries; those are still
rendered using trapezoids.

1 files changed, 0 insertions, 0 deletions

diff --git a/test/trap-clip.xlib.ref.png b/test/trap-clip.xlib.ref.png
new file mode 100644
index 00000000..2cbbdb76
--- /dev/null
+++ b/test/trap-clip.xlib.ref.png