re PR c++/10385 (Internal compiler error in build_up_reference, at cp/cvt.c:353, on invalid dynamic_cast)

	PR c++/10385
	* rtti.c (build_dynamic_cast_1): Check for invalid conversions
	before calling convert_to_reference.
	* cvt.c (convert_to_reference): Assert that reftype is a
	REFERENCE_TYPE.

	* g++.dg/conversion/dynamic1.C: New test.

From-SVN: r113084