* c-c++-common/gomp/flush-1.c: Add test case for 'seq_cst'.
* c-c++-common/gomp/flush-2.c: Add test case for 'seq_cst'.
* g++.dg/gomp/attrs-1.C: Adapt test to handle all flush clauses.
* g++.dg/gomp/attrs-2.C: Adapt test to handle all flush clauses.
* gfortran.dg/gomp/flush-1.f90: Add test case for 'seq_cst'.
* gfortran.dg/gomp/flush-2.f90: Add test case for 'seq_cst'.