* ports.h (scm_ptob_descriptor): include a write procedure again.

	* ports.h (scm_ptob_descriptor): include a write procedure again.
	it's more efficient for unbuffered fports (e.g., sockets.)

	* ports.c (scm_puts): use ptob->write.
	* vports.c (scm_make_sfptob): set write proc in ptob.
	* strports.c (scm_make_stptob): set write proc in ptob.
	* ports.c (write_void_port): new procedure.
	* vports.c (sf_write): new procedure.
	* ports.c (scm_lfwrite): use ptob->write.
	* strports.c (st_write): new procedure.
	* fports.c (fport_write): new procedure.
	(scm_make_fptob): set write in ptob to fport_write.
	* ports.h: prototype for scm_set_port_write.
	* ports.c (scm_make_port_type): initialise ptob write procedure.
	(scm_set_port_write): new proc.