[Ada] Valid postconditions incorrectly rejected.

[Ada] Valid postconditions incorrectly rejected.

gcc/ada/

	* sem_attr.adb (Analyze_Attribute_Old_Result): Permit an
	attribute reference inside a compiler-generated _Postconditions
	procedure. In this case, Subp_Decl is assigned the declaration
	of the enclosing subprogram.
	* exp_util.adb (Insert_Actions): When climbing up the tree
	looking for an insertion point, do not climb past an
	N_Iterated_Component/Element_Association, since this could
	result in inserting a reference to a loop parameter at a
	location outside of the scope of that loop parameter. On the
	other hand, be careful to preserve existing behavior in the case
	of an N_Component_Association node.