OpenMP/Fortran: Allow explicit map followed by implicit deep mapping [PR120505]

OpenMP/Fortran: Allow explicit map followed by implicit deep mapping [PR120505]

Consider the following source code, assuming tiles is allocatable:

```
!$omp target enter data map(var%tiles(1)%den1, var%tiles(1)%den2) !        (1)
[...]
!$omp target ! implicitly maps var, which triggers deep mapping of tiles   (2)
```

Each omp directive causes a run-time error in libgomp:
(1) libgomp: Mapped array elements must be the same (0x14d729c0 vs 0x14d72a18)
(2) libgomp: Trying to map into device [0x3704ca50..0x3704cb00) object when
             [0x3704ca50..0x3704caa8) is already mapped

Regarding (1), the OpenMP spec has the following restriction: "If multiple list
items are explicitly mapped on the same construct and have the same containing
array or have base pointers that share original storage, and if any of the list
items do not have corresponding list items that are present in the device data
environment prior to a task encountering the construct, then the list items must
refer to *the same array elements* of either the containing array or the
implicit array of the base pointers."
Because tiles is allocatable, we cannot prove at compile time that array
elements are the same, so the check is deferred to libgomp. But there the
condition enforcing that all addresses are the same is too strict, so this patch
relaxes it to only check that addresses are sorted in increasing order.

The OpenMP spec allows (2) as long as it is implicit, without extending the
original mapping. So this patch sets the GOMP_MAP_IMPLICIT flag appropriately
on deep maps at compile time to let libgomp know that it is fine.

This patch ensures that such user code is accepted by:
(1) Setting the GOMP_MAP_IMPLICIT flag appropriately on deep maps;
(2) Relaxing the restriction on struct mapping from different containing arrays,
so that the element index need not be the same, instead addresses must be sorted
in increasing order.

This fixes the two errors currently seen when running SPEC HPC clvleaf
benchmark. However, further mapping issues prevent the benchmark from running to
completion.

	PR fortran/120505

gcc/ChangeLog:

	* omp-low.cc (lower_omp_target): Set GOMP_MAP_IMPLICIT flag.

libgomp/ChangeLog:

	* target.c (gomp_map_vars_internal): Allow struct mapping from different
	containing array elements as long as adresses are in increasing order.
	* testsuite/libgomp.c-c++-common/map-arrayofstruct-2.c: Adjust
	dg-output.
	* testsuite/libgomp.c-c++-common/map-arrayofstruct-3.c: Likewise.
	* testsuite/libgomp.fortran/map-subarray-5.f90: Likewise.
	* testsuite/libgomp.fortran/map-subarray-10.f90: New test.
	* testsuite/libgomp.fortran/map-subarray-9.f90: New test.