fixed GTK styles handling:

1. don't modify the style unless something changed
2. use gtk_widget_modify_style instead of gtk_widget_set_style, the latter is not recommended by GTK+ developers


git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@27784 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/gtk1/bmpbuttn.cpp

@@ -193,12 +193,12 @@ wxString wxBitmapButton::GetLabel() const
     return wxControl::GetLabel();
 }
 
-void wxBitmapButton::ApplyWidgetStyle()
+void wxBitmapButton::DoApplyWidgetStyle(GtkRcStyle *style)
 {
     if ( !BUTTON_CHILD(m_widget) )
         return;
 
-    wxButton::ApplyWidgetStyle();
+    wxButton::DoApplyWidgetStyle(style);
 }
 
 void wxBitmapButton::OnSetBitmap()