Fortran/OpenMP: Fix handling of strictly structured blocks

Fortran/OpenMP: Fix handling of strictly structured blocks

For strictly structured blocks, a BLOCK was created but the code
was placed after the block the outer structured block. Additionally,
labelled blocks were mishandled. As the code is now properly in a
BLOCK, it solves additional issues.

gcc/fortran/ChangeLog:

	* parse.cc (parse_omp_structured_block): Make the user code end
	up inside of BLOCK construct for strictly structured blocks;
	fix fallout for 'section' and 'teams'.
	* openmp.cc (resolve_omp_target): Fix changed BLOCK handling
	for teams in target checking.

libgomp/ChangeLog:

	* testsuite/libgomp.fortran/strictly-structured-block-1.f90: New test.

gcc/testsuite/ChangeLog:

	* gfortran.dg/block_17.f90: New test.
	* gfortran.dg/gomp/strictly-structured-block-5.f90: New test.