rx: add rx_opaque and rx_identity exports

rx: add rx_opaque and rx_identity exports

	rx_opaque_new                           @289
	rx_opaque_alloc                         @290
	rx_opaque_populate                      @291
	rx_opaque_copy                          @292
	rx_opaque_freeContents                  @293
	rx_opaque_zeroFreeContents              @294
	rx_opaque_free                          @295
	rx_opaque_zeroFree                      @296
	rx_identity_match                       @297
	rx_identity_populate                    @298
	rx_identity_copy                        @299
	rx_identity_copyContents                @300
	rx_identity_new                         @301
	rx_identity_freeContents                @302
	rx_identity_free                        @303

Change-Id: Iaf52fdc65178db64c373b2f747ac133fdb713364
Reviewed-on: http://gerrit.openafs.org/3383
Reviewed-by: Jeffrey Altman <jaltman@openafs.org>
Tested-by: Jeffrey Altman <jaltman@openafs.org>