Make wxCompositeWindow ctor protected

As this class is only supposed to be used as a base class, its ctor
doesn't need to be, and hence ought not to be, public.

Also update an outdated comment stating that the ctor didn't do anything
when it, in fact, does perform an important task.

include/wx/compositewin.h

@@ -33,17 +33,6 @@ class wxCompositeWindow : public W
 public:
     typedef W BaseWindowClass;
 
-    // Default ctor doesn't do anything.
-    wxCompositeWindow()
-    {
-        this->Connect
-              (
-                  wxEVT_CREATE,
-                  wxWindowCreateEventHandler(wxCompositeWindow::OnWindowCreate)
-              );
-
-    }
-
     // Override all wxWindow methods which must be forwarded to the composite
     // window parts.
 
@@ -136,6 +125,17 @@ public:
         wxSetFocusToChild(this, NULL);
     }
 
+protected:
+    // Default ctor sets things up for handling children events correctly.
+    wxCompositeWindow()
+    {
+        this->Connect
+              (
+                  wxEVT_CREATE,
+                  wxWindowCreateEventHandler(wxCompositeWindow::OnWindowCreate)
+              );
+    }
+
 private:
     // Must be implemented by the derived class to return all children to which
     // the public methods we override should forward to.