* time/mktime.c (check_result): Use less-confusing report format.

* time/mktime.c (check_result): Use less-confusing report format.

	"long" -> "long int", as per usual GNU style.
	(main): Likewise.
	Don't loop if the iteration overflows time_t.
	Allow a negative step in the iteration.

	* time/mktime.c: Assume freestanding C89 or better.
	(HAVE_LIMITS_H, STDC_HEADERS) [defined _LIBC]: Remove;
	assume they're 1.
	(__P): Remove; not used.
	(CHAR_BIT, INT_MIN, INT_MAX): Remove; <limits.h> defines them.
	(mktime, not_equal_tm, print_tm, check_result, main): Use prototypes.
	Prototypes use const * where appropriate.
	(main) [DEBUG]: Fix typo in testing code uncovered by above changes,
	which caused the testing code to dump core on some hosts.