Added reverse iterator methods.
Added reverse iterator methods.


OPENDAP/libdap,OPENDAP/libdap4,OPENDAP/libdap,OPENDAP/libdap4,OPENDAP/libdap,OPENDAP/libdap4,OPENDAP/libdap4,OPENDAP/libdap4,OPENDAP/libdap4,OPENDAP/libdap