[ruby] check whether object is of RTypedData using RTYPEDDATA_P.

Examples/test-suite/ruby_rdata.i

@@ -0,0 +1,20 @@
+%module ruby_rdata
+
+%{
+
+  class C {};
+
+  int take_proc_or_cpp_obj_and_ret_1(VALUE obj) {
+    return 1;
+  }
+
+  int take_proc_or_cpp_obj_and_ret_1(class C) {
+    return 1;
+  }
+
+%}
+
+class C {};
+
+int take_proc_or_cpp_obj_and_ret_1(VALUE);
+int take_proc_or_cpp_obj_and_ret_1(C);