Commit the darwin.c changes I missed in the last commit, for calling
setVisualConfigs().
(cherry picked from commit eb3c014e1710bf0b93bda10ddb9b795cd150d02d)
Add a setVisualConfigs that is called before the fbScreenInit, to setup the __GLXvisualConfigs.
(cherry picked from commit fc86f9e4482043eca76d9d7a96e166be1aabf674)