* libguile/ephemerons.h:
* libguile/ephemerons.c (scm_c_ephemeron_load, scm_c_ephemeron_push):
New routines.
* libguile/ioext.c (scm_fdes_to_ports): Rework in terms of
scm_c_port_for_each.
* libguile/ports-internal.h (struct scm_t_port): Add pointer to entry on
weak ports list, so that we can cancel it easily.
* libguile/ports.c (release_port): Mark weak ports list entry as dead.
(all_ports_needing_close, for_each_port_needing_close): Rework as
ephemeron chain.
(scm_c_make_port_with_encoding, close_port, scm_c_port_for_each): Adapt
API.
(scm_init_ports): No more weak set.
* libguile/ephemerons.c (scm_from_ephemeron, scm_to_ephemeron):
(scm_from_ephemeron_table, scm_to_ephemeron_table): New interfaces.
(scm_c_ephemeron_table_copy): Rename from
scm_c_ephemeron_hash_table_copy, as it's not specific to hash tables.
* libguile/fluids.h:
* libguile/fluids.c (restore_dynamic_state, save_dynamic_state)
(saved_dynamic_state_ref, fluid_set_x, fluid_ref)
(scm_fluid_ref_star, scm_i_make_initial_dynamic_state): Use ephemeron
hash tables.
