Fortran: update DATE_AND_TIME intrinsic for Fortran 2018 [PR96580]

Fortran 2018 allows a non-default integer kind for its VALUES argument if
it has a decimal exponent range of at least four.  Update checks, library
implementation and documentation.

gcc/fortran/ChangeLog:

	PR fortran/96580
	* check.cc (array_size_check): New helper function.
	(gfc_check_date_and_time): Use it for checking minimum size of
	VALUES argument.  Update kind check to Fortran 2018.
	* intrinsic.texi: Fix documentation of DATE_AND_TIME.

libgfortran/ChangeLog:

	PR fortran/96580
	* intrinsics/date_and_time.c (date_and_time): Handle VALUES argument
	for kind=2 and kind=16 (if available).

gcc/testsuite/ChangeLog:

	PR fortran/96580
	* gfortran.dg/date_and_time_2.f90: New test.
	* gfortran.dg/date_and_time_3.f90: New test.
	* gfortran.dg/date_and_time_4.f90: New test.