[Ada] Improve unnesting of indexed references

[Ada] Improve unnesting of indexed references

2018-05-28  Richard Kenner  <kenner@vlsi1.ultra.nyu.edu>

gcc/ada/

	* exp_unst.adb (Check_Static_Type): Add argument to indicate node to be
	replaced, if any; all callers changed.
	(Note_Uplevel_Ref): Likewise.  Also replace reference to deferred
	constant with private view so we take the address of that entity.
	(Note_Uplevel_Bound): Add argument to indicate node to be replaced, if
	any; all callers changed.  Handle N_Indexed_Component like
	N_Attribute_Reference.  Add N_Type_Conversion case.
	(Visit_Node): Indexed references can be uplevel if the type isn't
	static.
	(Unnest_Subprograms): Don't rewrite if no reference given.  If call has
	been relocated, set first_named pointer in original node as well.

From-SVN: r260830