due to changes in libpng's API as of 1.2.30, cairo needs to provide an additional function callback to libpng. This was added to 1.6.4-r1. Before any libpng 1.2.30 or higher goes stable this needs to happen, otherwise any app that uses PNGs and cairo (read: any GTK+ app using PNGs) will segfault.
ppc and ppc64 stable
alpha/ia64/sparc/x86 stable
Stable for HPPA.
amd64 stable
arm/sh stable by vapier