* gc.c (scm_must_malloc): changed the comment explaining when

	* gc.c (scm_must_malloc): changed the comment explaining when
	scm_must variants of malloc/free etc., should be used, based on
	explanation from Dirk Herrmann.
	* fports.c (scm_fport_buffer_add): use FUNC_NAME instead of a local
	string with procedure name.  use scm_must_malloc instead of malloc.
	(scm_setvbuf, scm_fdes_to_port, fport_close): use scm_must variants
	of malloc/free.
	* ports.c (scm_add_to_port_table, scm_remove_from_port_table,
	scm_ungetc): use scm_must variants of malloc/realloc/free.
	(scm_add_to_port_table, scm_ungetc): define FUNC_NAME.