[Ada] Fix internal error on string type comparision with predicate

[Ada] Fix internal error on string type comparision with predicate

gcc/ada/

	* freeze.adb (Has_Decl_In_List): New predicate to check that an
	entity is declared in a list of nodes.
	(Freeze_Expression): Use it to deal with Expression_With_Actions,
	short-circuit expression, if- and case-expression and ensure that
	the freeze node is put onto their Actions list if the entity is
	declared locally.