Merge remote-tracking branch 'origin/shared_ptr_const_conv' into shared_ptr_derived_2

Lib/ruby/std_shared_ptr.i

@@ -83,6 +83,14 @@ namespace swig {
       }
     }
   };
- }
+
+  template<class Type>
+  struct traits_from<std::shared_ptr<const Type> > {
+    static VALUE from(const std::shared_ptr<const Type>& val) {
+      std::shared_ptr<Type> p = std::const_pointer_cast<Type>(val);
+      return swig::from(p);
+    }
+  };
+}
 #endif
 %}