[cairo] Bug: Crash in cairo-1.9.8

[cu]

Note: this does not happen on Linux. Also, the code is compiled using
arch of i386 on Mac (i.e. not 64 bit) - not sure if this makes a difference.

cu wrote:
> The following drawing code crashes (inside pixman) when compiled against
> cairo-1.9.8 (pixman versions of 0.17.14 and 0.18.2 tested). The crash
> does not occur using cairo 1.9.6 (with a few patches). Tested on MacOS
> 10.6.
>