Restructure wxNotificationMessage.

wxNotificationMessage has been refactored to always use wxNotificationMessageImpl (this was previously already done in the MSW implementation)

This adds various features and fixes to wxNotificationMessage:
- OS X Notification Center implementation
- Generic "toast" notifications
- SetIcon() to specify a custom icon
- AddAction() to add actions to notifications
- Events to get notify of notification clicks, dismiss or actions

include/wx/generic/notifmsg.h

@@ -10,8 +10,6 @@
 #ifndef _WX_GENERIC_NOTIFMSG_H_
 #define _WX_GENERIC_NOTIFMSG_H_
 
-class wxNotificationMessageDialog;
-
 // ----------------------------------------------------------------------------
 // wxGenericNotificationMessage
 // ----------------------------------------------------------------------------
@@ -19,40 +17,29 @@ class wxNotificationMessageDialog;
 class WXDLLIMPEXP_ADV wxGenericNotificationMessage : public wxNotificationMessageBase
 {
 public:
-    wxGenericNotificationMessage() { Init(); }
-    wxGenericNotificationMessage(const wxString& title,
-                                 const wxString& message = wxString(),
-                                 wxWindow *parent = NULL,
-                                 int flags = wxICON_INFORMATION)
-        : wxNotificationMessageBase(title, message, parent, flags)
+    wxGenericNotificationMessage()
     {
         Init();
     }
 
-    virtual ~wxGenericNotificationMessage();
-
-
-    virtual bool Show(int timeout = Timeout_Auto);
-    virtual bool Close();
+    wxGenericNotificationMessage(const wxString& title,
+                                 const wxString& message = wxString(),
+                                 wxWindow *parent = NULL,
+                                 int flags = wxICON_INFORMATION)
+    {
+        Init();
+        Create(title, message, parent, flags);
+    }
 
     // generic implementation-specific methods
 
     // get/set the default timeout (used if Timeout_Auto is specified)
-    static int GetDefaultTimeout() { return ms_timeout; }
+    static int GetDefaultTimeout();
     static void SetDefaultTimeout(int timeout);
 
 private:
     void Init();
 
-
-    // default timeout
-    static int ms_timeout;
-
-    // notification message is represented by a modeless dialog in this
-    // implementation
-    wxNotificationMessageDialog *m_dialog;
-
-
     wxDECLARE_NO_COPY_CLASS(wxGenericNotificationMessage);
 };