[Ada] Add a new Is_Activation_Record flag on IN parameters

[Ada] Add a new Is_Activation_Record flag on IN parameters

2018-05-24  Ed Schonberg  <schonberg@adacore.com>

gcc/ada/

	* einfo.ads, einfo.adb (Is_Activation_Record): New flag on
	in_parameters, used when unesting subprograms for LLVM, to indicate
	that a generated parameter carries the activation record from the
	enclosing subprogram.
	* exp_unst.adb (Check_Static_Type): Handle array attributes of types
	whose bounds may contain up-level references that need to be added to
	an activation recoord.
	(Add_Extra_Formal): Set Is_Activation_Record on new formal.

From-SVN: r260666