gdk-pixbuf: Upgrade 2.36.6 -> 2.36.8

gdk-pixbuf: Upgrade 2.36.6 -> 2.36.8

Smallish releases with bug fixes and minor improvements.

shared-mime-info is now always used for image type sniffing.
The dependency does not seem to currently be a build-time dependency
but configure.ac does check for it: I took the easy route and just
added shared-mime-info to DEPENDS as well.

Signed-off-by: Jussi Kukkonen <jussi.kukkonen@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>