Fortran version of commit 5079b778

gcc/fortran/ChangeLog:

	* match.h (gfc_match_omp_nothing): New.
	* openmp.c (gfc_match_omp_nothing): New.
	* parse.c (decode_omp_directive): Match 'nothing' directive.

gcc/testsuite/ChangeLog:

	* gfortran.dg/nothing-1.f90: New test.
	* gfortran.dg/nothing-2.f90: New test.