Some time-handling patches from Paul Eggert:

Some time-handling patches from Paul Eggert:
	* editfns.c (Fcurrent_time_zone): Take an optional argument specifying
	what (absolute) time should be used to determine the current time zone.
	Yield just offset and name of time zone, including DST correction.
	Yield time zone offset in seconds, not minutes.
	(lisp_time_argument, difftm): New functions.
	(Fcurrent_time_string): Use lisp_time_argument.
	* systime.h (EMACS_CURRENT_TIME_ZONE, EMACS_GET_TZ_OFFSET,
	EMACS_GET_TZ_NAMES): Remove.
	* config.h.in: Add HAVE_TM_ZONE.