maint: let libtool deal with setting -rpath linker option * configure.ac (--enable-rpath): Delete option handler. (RLD_FLAG): Delete variable and all uses. * common.mk (RLD_FLAG): Don't substitute it. (do_subst_config_vals): Don't substitute OCTAVE_CONF_RLD_FLAG. * oct-conf.h.in (OCTAVE_CONF_RLD_FLAG): Delete definition. * toplev.cc (octave_config_info): Delete RLD_FLAG from the list. * libcruft/Makefile.am, liboctave/Makefile.am, src/Makefile.am, src/link-deps.mk: Don't add RLD_FLAG to link options.