Removed GetClass from Cocotron. This change requires updated Cocotron runtime.
(Like the one here: git@github.com:rafcabezas/glennganz-cocotron1-clang.git)
But minimally replace objc_lookUpClass in objc_class.m with:
//clang support
static inline __objc_lookup_class(const char *className) {
    id result;

    pthread_mutex_lock(&classTableLock);
    result=OBJCHashValueForKey(OBJCClassTable(),className);
    pthread_mutex_unlock(&classTableLock);

    return result;
}

id objc_lookup_class(const char *className) {
    return __objc_lookup_class(className);
}

id objc_lookUpClass(const char *className) {
    return __objc_lookup_class(className);
}