[Ada] Fix iterated element association loop var escaping loop scope

[Ada] Fix iterated element association loop var escaping loop scope

Fix the escaping of the loop variable from the loop scope in both forms
of iterated element associations (i.e. "for J in ..." and "for J of
..."). Create a dedicated scope around the analyses of both loops. Also
create a copy of the Loop_Parameter_Specification instead of analyzing
(and modifying) the original Tree as it will be reanalyzed later.

gcc/ada/

	* sem_aggr.adb (Resolve_Iterated_Association): Create scope
	around N_Iterated_Element_Association handling. Analyze a copy
	of the Loop_Parameter_Specification. Call Analyze instead
	Analyze_* to be more homogeneous.
	(Sem_Ch5): Remove now unused package.