[Ada] Unnesting problems with expansion of Loop_Entry attribute

[Ada] Unnesting problems with expansion of Loop_Entry attribute

2020-06-03  Gary Dismukes  <dismukes@adacore.com>

gcc/ada/

	* exp_attr.adb (Expand_Loop_Entry_Attribute): Revise loop that
	resets the scopes of entities associated with Loop_Id to the
	scope of the new function, so the resetting is not restricted to
	itypes, but excludes loop parameters and the function entity
	itself. However, this fix is believed to be incomplete and a ???
	comment is added to indicate that.