ada: Fix resolving tagged operations in array aggregates

ada: Fix resolving tagged operations in array aggregates

In the Two_Pass_Aggregate_Expansion we were removing
all of the entity links in the Iterator_Specification
to avoid reusing the same Iterator_Definition in both
loops.

However this approach was also breaking the links to
calls with dot notation that had been transformed to
the regular call notation.

In order to circumvent this, explicitly create new
identifier definitions when copying the
Iterator_Specfications for both of the loops.

gcc/ada/

	* exp_aggr.adb (Two_Pass_Aggregate_Expansion):
	Explicitly create new Defining_Iterators for both
	of the loops.