open-babel: 2.3.2 patch to fix pybel's Molecule.draw + fix for Cairo

Added a patch that fixes Molecule.draw() in pybel.py (similar to upstream commit f59c4a630cf753723d1318c40479d48b7507e1c). open-babel have fairly slow releases, so I thought there was a point to include the fix via a patch while waiting for the next release. The changes will be included in 2.3.3 so then the patch is obsolete.
Also fixed the inclusion of the Cairo library and includes. Earlier the CMake directives were poiting to locations within the open-babel installation. There also seemed to be a confusion between strings and arguments, giving cmake problems to understand the directive.