[Ada] Incorrect Dynamic_Predicate results for static arguments

[Ada] Incorrect Dynamic_Predicate results for static arguments

gcc/ada/

	* exp_ch6.adb (Can_Fold_Predicate_Call): Do not attempt folding
	if there is more than one predicate involved. Recall that
	predicate aspect specification are additive, not overriding, and
	that there are three different predicate
	aspects (Dynamic_Predicate, Static_Predicate, and the
	GNAT-defined Predicate aspect). These various ways of
	introducing multiple predicates are all checked for.  A new
	nested function, Augments_Other_Dynamic_Predicate, is
	introduced.
	* sem_ch4.adb
	(Analyze_Indexed_Component_Form.Process_Function_Call): When
	determining whether a name like "X (Some_Discrete_Type)" might
	be interpreted as a slice, the answer should be "no" if the
	type/subtype name denotes the current instance of type/subtype.