Disallow conversion from `super`

test/libsolidity/syntaxTests/conversion/not_allowed_conversion_from_super.sol

@@ -0,0 +1,15 @@
+contract S
+{
+	int o;
+	function foo() public returns (int) { return o = 3; }
+}
+
+contract B is S
+{
+	function fii() public
+	{
+		o = S(super).foo();
+	}
+}
+// ----
+// TypeError: (129-137): Explicit type conversion not allowed from "contract super B" to "contract S".