[Ada] Wrappers of access-to-subprograms with pre/post conditions

[Ada] Wrappers of access-to-subprograms with pre/post conditions

gcc/ada/

	* sem_ch3.adb (Build_Access_Subprogram_Wrapper): Decorate the
	wrapper with attribute Is_Wrapper, and move its declaration to
	the freezing actions of its type declaration; done to facilitate
	identifying it at later stages to avoid handling it as a
	primitive operation of a tagged type; otherwise it may be
	handled as a dispatching operation and erroneously registered in
	a dispatch table.
	(Make_Index): Add missing decoration of field Parent.
	* sem_disp.adb (Check_Dispatching_Operation): Complete
	decoration of late-overriding dispatching primitives.
	(Is_Access_To_Subprogram_Wrapper): New subprogram.
	(Inherited_Subprograms): Prevent cascaded errors; adding missing
	support for private types.
	* sem_type.adb (Add_One_Interp): Add missing support for the
	first interpretation of a primitive of an inmediate ancestor
	interface.
	* sem_util.adb (Check_Result_And_Post_State_In_Pragma): Do not
	report missing reference in postcondition placed in internally
	built wrappers.
	* exp_disp.adb (Expand_Dispatching_Call): Adding assertion.