Include <string.h> even if !DEBUG. (From glibc.)

Include <string.h> even if !DEBUG.  (From glibc.)
(ranged_convert): Don't save conversion in a temporary struct.
This causes a warning with GCC 4.0.0, and anyway in the typical
case it's not worth the extra 100 bytes or so of code.
(ranged_convert, __mktime_internal): When calling a function via a
pointer P, use P () rather than (*P) (), as we now assume C89 or better.