Revert "Only permit threadsafe pixbuf loaders"
Revert "Only permit threadsafe pixbuf loaders"

This reverts commit 9333f2da7ea92d475a45861fcf47dc385a783171.
It didn't work as intended and needs more work.

GNOME/librsvg,GNOME/librsvg,GNOME/librsvg,GNOME/librsvg