ada: Fix crash on semi-recursive call in access-to-subprogram contract

ada: Fix crash on semi-recursive call in access-to-subprogram contract

Calls to access-to-subprogram from its own pre/post aspects are rejected
as illegal, e.g.:

   type F is access function (X : Natural) return Boolean with
     Pre => F.all (X);

but they caused an assertion failure in detection of recursive calls.

Now they are properly recognized as recursive, but the error is
suppressed, because it has been already posted at the call node.

gcc/ada/

	* sem_res.adb (Invoked_With_Different_Arguments): Use Get_Called_Entity,
	which properly deals with calls via an access-to-subprogram; fix
	inconsistent use of a Call object declared in enclosing subprogram.