fix signature of CallStack.toString() for macro time

Author: RealyUniqueName

format/php7/haxe/CallStack.hx

@@ -127,6 +127,6 @@ class CallStack {
 #else
 	static public function callStack():Array<StackItem> throw "Not implemented. See https://github.com/RealyUniqueName/JStack/issues/10";
 	static public function exceptionStack():Array<StackItem> throw "Not implemented. See https://github.com/RealyUniqueName/JStack/issues/10";
-	static public function toString():String throw "Not implemented. See https://github.com/RealyUniqueName/JStack/issues/10";
+	static public function toString( stack : Array<StackItem> ):String throw "Not implemented. See https://github.com/RealyUniqueName/JStack/issues/10";
 #end
 }