c++: fix conversion issues

c++: fix conversion issues

Some issues caught by a check from another patch:

In the convert_like_internal bad_p handling, we are iterating from outside
to inside, so once we recurse into convert_like we need to stop looping.

In build_ramp_function, we're assigning REFERENCE_TYPE things, so we need to
build the assignment directly rather than rely on functions that implement
C++ semantics.

In omp_declare_variant_finalize_one, the parameter object building failed to
handle reference parms, and it seems simpler to just use build_stub_object
like other parts of the compiler.

gcc/cp/ChangeLog:

	* call.cc (convert_like_internal): Add missing break.
	* coroutines.cc (cp_coroutine_transform::build_ramp_function): Build
	INIT_EXPR directly.
	* decl.cc (omp_declare_variant_finalize_one): Use build_stub_object.

gcc/testsuite/ChangeLog:

	* g++.dg/gomp/declare-variant-3.C: Don't depend on expr dump.
	* g++.dg/gomp/declare-variant-5.C: Likewise.