class.c (dfs_ctor_vtable_bases_queue_p): Always walk into the shared virtual base, so preserving inheritance graph order.

cp:
	* class.c (dfs_ctor_vtable_bases_queue_p): Always walk into
	the shared virtual base, so preserving inheritance graph order.
testsuite:
	* g++.dg/abi/vbase8-22.C: New test.

From-SVN: r44506