[Ada] Wrong address for class-wide interface access conversion

[Ada] Wrong address for class-wide interface access conversion

The compiler generates wrong code on instantiations of package
Address_To_Access_Conversions when the generic formal is a class-wide
interface type; this causes wrong dispatching calls when the
access-to-class-wide-interface object returned by To_Pointer is used to
dispatch a call.

gcc/ada/

	* exp_attr.adb (Expand_N_Attribute_Reference): The expansion of
	'Address in a call to an instantiation of the implicit
	subprogram To_Pointer with a class-wide interface type target
	requires adding an implicit type conversion to force
	displacement of the "this" pointer.