OpenMP: Fix bogus diagnostics with intervening code [PR121452]

OpenMP: Fix bogus diagnostics with intervening code [PR121452]

The introduction in r14-3488-ga62c8324e7e31a of OMP_STRUCTURED_BLOCK (to
diagnose invalid intervening code) caused a regression rejecting the valid use
of the Fortran CONTINUE statement to end a collapsed loop.
This patch fixes the incorrect error checking in the OMP lowering pass. It also
fixes a check in the Fortran front end that erroneously rejects a similar
statement in an ordered loop.

Co-authored by: Tobias Burnus <tburnus@baylibre.com>

	PR fortran/121452

gcc/fortran/ChangeLog:

	* openmp.cc (resolve_omp_do): Allow CONTINUE as end statement of a
	perfectly nested loop.

gcc/ChangeLog:

	* omp-low.cc (check_omp_nesting_restrictions): Accept an
	OMP_STRUCTURED_BLOCK in a collapsed simd region and in an ordered loop.

gcc/testsuite/ChangeLog:

	* c-c++-common/gomp/pr121452-1.c: New test.
	* c-c++-common/gomp/pr121452-2.c: New test.
	* gfortran.dg/gomp/pr121452-1.f90: New test.
	* gfortran.dg/gomp/pr121452-2.f90: New test.
	* gfortran.dg/gomp/pr121452-3.f90: New test.