Error messages from libbson and libmongoc changed between 1.5.0 and 1.6.0, which poses a problem for Fedora packaging. Without upgrading v1.2 to support libbson/libmongoc 1.6.0 (already handled in PHPC-892 for v1.3), we should at least make our test suite compatible with both variations.

This will require testing with libbson and libmongoc system libraries instead of bundled versions.