Ensure that info bar message uses the set font/colours in wxGTK.

Propagate the font and colours set on wxInfoBar window itself to its label in
the native GTK implementation.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@62286 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/gtk/infobar.h

@@ -55,6 +55,7 @@ public:
 
 protected:
     virtual bool GTKShouldConnectSizeRequest() const { return false; }
+    virtual void DoApplyWidgetStyle(GtkRcStyle *style);
 
 private:
     void Init() { m_impl = NULL; }