* ports.h (scm_port_table): remove file_name member for now, it seems

	* ports.h (scm_port_table): remove file_name member for now, it seems
	undesirable.
	* fports.c (scm_open_file): don't set file_name in PTAB.
	(prinfport): don't use file_name in PTAB.
	* ioext.c (scm_sys_duplicate_port): don't set file_name in PTAB.
	* ports.c (scm_add_to_port_table): don't intialize file_name.
	(scm_port_file_name): remove for now.
	* gc.c (scm_gc_mark): don't mark PTAB file_name.

	* fports.h (scm_mkfile): prototype deleted.
	* fports.c (scm_mkfile): merged into scm_open_file to simplify.