Rework external function handlers (#4599)

Instead of a fixed number of arguments, a call info structure is passed
to the handlers, which can be extended in the future without breaknig the
API. This structure holds new.target value, so its getter function is removed.

JerryScript-DCO-1.0-Signed-off-by: Zoltan Herczeg zherczeg.u-szeged@partner.samsung.com

tests/unit-core/test-native-instanceof.c

@@ -19,13 +19,11 @@
 static const char instanceof_source[] = "var x = function(o, c) {return (o instanceof c);}; x";
 
 static jerry_value_t
-external_function (const jerry_value_t function_obj,
-                   const jerry_value_t this_arg,
+external_function (const jerry_call_info_t *call_info_p,
                    const jerry_value_t args_p[],
                    const jerry_size_t args_count)
 {
-  (void) function_obj;
-  (void) this_arg;
+  (void) call_info_p;
   (void) args_p;
   (void) args_count;