OpenMP/C++: Permit mapping classes with virtual members [PR102204]

	PR c++/102204
gcc/cp/ChangeLog:

	* decl2.cc (cp_omp_mappable_type_1): Remove check for virtual
	members as those are permitted since OpenMP 5.0.

libgomp/ChangeLog:

	* testsuite/libgomp.c++/target-virtual-1.C: New test.

gcc/testsuite/ChangeLog:

	* g++.dg/gomp/unmappable-1.C: Remove previously expected dg-message.