This routine initializes a read-write lock object. The routine
    initializes the tis_rwlock_t structure that holds the object's
    lock states.

    To destroy a read-write lock object, call the tis_rwlock_
    destroy() routine.

                                   NOTE

       The tis read-write lock has no relationship to the Single
       UNIX Specification, Version 2 (SUSV2, or UNIX98) read-
       write lock routines (such as pthread_rwlock_init()). The
       tis_rwlock_t type, in particular, cannot be used with the
       pthread read-write lock functions, nor can a pthread_rwlock_
       t type be used with the tis read-write lock functions.