ada: Cannot override inherited function with controlling result

ada: Cannot override inherited function with controlling result

When a package has the declaration of a derived tagged
type T with private null extension that inherits a public
function F with controlling result, and a derivation of T
is declared in the public part of another package, overriding
function F may be rejected by the compiler.

gcc/ada/

	* sem_disp.adb (Find_Hidden_Overridden_Primitive): Check
	public dispatching primitives of ancestors; previously,
	only immediately-visible primitives were checked.