common: Add new function isodate_human_to_tm
* common/gettime.c (isotime_human_p): Add arg date_only. (isodate_human_to_tm): New. * common/t-gettime.c (test_isodate_human_to_tm): New. (main): Call new test.
This function in intended as replacement for
strptime (foo, "%Y-%m-%d", &bar)
which is not available under Windows.