ada: Etype missing for raise expression

If the primitive equality operator of the component type of an array type is
abstract, then a call to that abstract function raises Program_Error (when
such a call is legal). The FE generates a raise expression to implement this.
That raise expression is an expression so it should have a valid Etype.

gcc/ada/

	* exp_ch4.adb (Build_Eq_Call): In the abstract callee case, copy
	the Etype of the callee onto the Make_Raise_Program_Error result.