testsuite/libgomp.oacc-fortran: Update dg-output to fix GCN

testsuite/libgomp.oacc-fortran:  Update dg-output to fix GCN

        * testsuite/libgomp.oacc-fortran/error_stop-1.f: Also don't
        expect dg-output of 'Error termination.' for GCN.
        * testsuite/libgomp.oacc-fortran/error_stop-2.f: Likewise.
        * testsuite/libgomp.oacc-fortran/error_stop-3.f: Likewise.

Plus: Fix date of a previous commit in:
        * gcc/fortran/ChangeLog
        * gcc/testsuite/ChangeLog

From-SVN: r278986