c++: ICE with computed gotos [PR115469]

c++: ICE with computed gotos [PR115469]

This is a low-prio crash on invalid code where we ICE on a VAR_DECL
with erroneous type.  I thought I'd try to avoid putting such decls
into ->names and ->names_in_scope but that sounds riskier than the
following cleanup.

	PR c++/115469

gcc/cp/ChangeLog:

	* decl.cc (automatic_var_with_nontrivial_dtor_p): New.
	(poplevel_named_label_1): Use it.
	(check_goto_1): Likewise.

gcc/testsuite/ChangeLog:

	* g++.dg/ext/label17.C: New test.