openacc: Dereference BT_CLASS data pointers but not BT_DERIVED pointers

openacc: Dereference BT_CLASS data pointers but not BT_DERIVED pointers

The stanza in gfc_trans_omp_clauses that handles derived type members
that are themselves derived type pointers or class pointers now adds
an explicit dereference only for the latter. The former is already
dereferenced transparently in gfc_conv_component_ref.

gcc/fortran/
	* trans-openmp.c (gfc_trans_omp_clauses): Fix dereferencing for
	BT_DERIVED members.

gcc/testsuite/
	* gfortran.dg/goacc/derived-classtypes-1.f95: New test.