ada: Fix internal error on aspect in complex object declaration

The sufficient conditions are that the aspect be deferred and the object be
rewritten as a renaming because of the complex initialization expression.

gcc/ada/ChangeLog:

	* gcc-interface/trans.cc (gnat_to_gnu)
	<N_Object_Renaming_Declaration>: Deal with objects whose elaboration
	is deferred.
	(process_freeze_entity): Deal with renamed objects whose elaboration
	is deferred.