Remove jerry_get_arg_value function. (#2425)

Remove automatic conversion of errors. Errors are
primary values, just like numbers or strings.

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

tests/unit-ext/test-ext-module-empty.c

@@ -39,6 +39,7 @@ main (int argc, char **argv)
   TEST_ASSERT (jerry_value_is_error (module));
 
   /* Retrieve the error message. */
+  module = jerry_get_value_from_error (module, true);
   jerry_value_t prop_name = jerry_create_string ((const jerry_char_t *) "message");
   jerry_value_t prop = jerry_get_property (module, prop_name);