c++: local class in nested generic lambda [PR109241]

c++: local class in nested generic lambda [PR109241]

The earlier fix for PR109241 avoided the crash by handling a type with no
TREE_BINFO.  But we want to move toward doing the partial substitution of
classes in generic lambdas, so let's take a step in that direction.

	PR c++/109241

gcc/cp/ChangeLog:

	* pt.cc (instantiate_class_template): Do partially instantiate.
	(tsubst_expr): Do call complete_type for partial instantiations.