Fortran/openmp: Fix '!$omp end'

Fortran/openmp: Fix '!$omp end'

gcc/fortran/ChangeLog:

	* parse.c (decode_omp_directive): Fix permitting 'nowait' for some
	combined directives, add missing 'omp end ... loop'.
	(gfc_ascii_statement): Fix ST_OMP_END_TEAMS_LOOP result.
	* openmp.c (resolve_omp_clauses): Add missing combined loop constructs
	case values to the 'if(directive-name: ...)' check.
	* trans-openmp.c (gfc_split_omp_clauses): Put nowait on target if
	first leaf construct accepting it.

gcc/testsuite/ChangeLog:

	* gfortran.dg/gomp/unexpected-end.f90: Update dg-error.
	* gfortran.dg/gomp/clauses-1.f90: New test.
	* gfortran.dg/gomp/nowait-2.f90: New test.
	* gfortran.dg/gomp/nowait-3.f90: New test.