[Ada] Transient scope cleanup

[Ada] Transient scope cleanup

gcc/ada/

	* sem.ads (Node_To_Be_Wrapped): Minor comment fix.
	* exp_ch7.adb (Establish_Transient_Scope): Misc cleanups and
	comment improvements.
	(Set_Node_To_Be_Wrapped): Remove -- not worth putting this code
	in a separate procedure, called only once.
	* sem_util.adb (Requires_Transient_Scope): Assert that our
	parameter has the right Kind. It probably shouldn't be E_Void,
	but that is passed in in some cases.
	(Ensure_Minimum_Decoration): Move the call later, so we know Typ
	is Present, and remove "if Present (Typ)" from this procedure.
	* exp_aggr.adb (Convert_To_Assignments): Use membership test,
	and avoid the "if False" idiom.
	(Expand_Array_Aggregate): Remove a ??? comment.
	* sem_ch8.adb (Push_Scope): Take advantage of the full coverage
	rules for aggregates.
	* sem_res.adb (Resolve_Declare_Expression): Remove test for
	Is_Type -- that's all it can be.  Use named notation in call to
	Establish_Transient_Scope.
	* libgnat/a-cdlili.adb (Adjust): Remove redundant code.
	(Clear): Remove "pragma Warnings (Off);", which wasn't actually
	suppressing any warnings.