openacc: Allow strided arrays in update directives

openacc: Allow strided arrays in update directives

OpenACC 3.0 ("2.14.4. Update Directive") states:

  Noncontiguous subarrays may appear. It is implementation-specific
  whether noncontiguous regions are updated by using one transfer for
  each contiguous subregion, or whether the non-contiguous data is
  packed, transferred once, and unpacked, or whether one or more larger
  subarrays (no larger than the smallest contiguous region that contains
  the specified subarray) are updated.

This patch relaxes some conditions in the Fortran front-end so that
strided accesses are permitted for update directives.

gcc/fortran/
	* openmp.c (resolve_omp_clauses): Omit OpenACC update in
	contiguity check and stride-specified error.

gcc/testsuite/
	* gfortran.dg/goacc/array-with-dt-2.f90: New test.

libgomp/
	* testsuite/libgomp.oacc-fortran/array-stride-dt-1.f90: New test.