Free an rbhash structure. Note that this function will not free the
individual entries still in the hash table, and they will likely
be lost forever. It is reecommended that the RBHASH_FOREACH macro
(see rbhash(3) ) be used to free all the entry structures in the
table prior to calling rbhash_free(3) .
RETURN VALUE
This function returns no value, and will always succeed.
