Change GEOSMessageHandler_r to no longer be a variadic function
Rename initGEOS_r_v2 to GEOS_init_r
Add GEOS_finish_r
Rename GEOSContext_setNoticeHandler_r_v2 to GEOSContext_setNoticeMessageHandler_r
Rename GEOSContext_setErrorHandler_r_v2 to GEOSContext_setErrorMessageHandler_r