Add basic tests for dispathing init_with based on their number of args

tests/test-mcore.c

@@ -295,6 +295,12 @@ static void test_oplist(void)
 
 #define A5   (NAME(1))
   assert (M_GET_NAME A5);
+
+#define A6  (NAME(A6), INIT_WITH(API_1(M_INIT_WITH_NVAR)))
+#define A6_init_with_1(x) 1
+#define A6_init_with_2(x, y) 0
+  assert (M_CALL_INIT_WITH (A6, 0));
+  assert (!M_CALL_INIT_WITH (A6, 0, 0));
 }
 
 static void test_cast(void)