Fix harmless warnings in samples (wxGTK)

Under wxGTK, wxAboutBox with no parent raises a warning "GtkDialog mapped without a transient parent".

samples/animate/anitest.cpp

@@ -261,7 +261,7 @@ void MyFrame::OnAbout(wxCommandEvent& WXUNUSED(event) )
     info.AddDeveloper(wxT("Guillermo Rodriguez Garcia"));
     info.AddDeveloper(wxT("Francesco Montorsi"));
 
-    wxAboutBox(info);
+    wxAboutBox(info, this);
 }
 
 #if wxUSE_FILEDLG

samples/collpane/collpane.cpp

@@ -268,7 +268,7 @@ void MyFrame::OnAbout(wxCommandEvent& WXUNUSED(event) )
     info.SetDescription(_("This sample program demonstrates usage of wxCollapsiblePane"));
     info.SetCopyright(wxT("(C) 2006 Francesco Montorsi <frm@users.sourceforge.net>"));
 
-    wxAboutBox(info);
+    wxAboutBox(info, this);
 }
 
 void MyFrame::OnCollapseUpdateUI(wxUpdateUIEvent& event)

samples/dataview/dataview.cpp

@@ -955,7 +955,7 @@ void MyFrame::OnAbout( wxCommandEvent& WXUNUSED(event) )
     info.AddDeveloper("Robert Roebling");
     info.AddDeveloper("Francesco Montorsi");
 
-    wxAboutBox(info);
+    wxAboutBox(info, this);
 }
 
 

samples/grid/griddemo.cpp

@@ -1375,7 +1375,7 @@ void GridFrame::About(  wxCommandEvent& WXUNUSED(ev) )
     // work with it for some reason) is moved over it.
     aboutInfo.SetWebSite(wxT("http://www.wxwidgets.org"));
 
-    wxAboutBox(aboutInfo);
+    wxAboutBox(aboutInfo, this);
 }
 
 

samples/treelist/treelist.cpp

@@ -569,7 +569,7 @@ void MyFrame::OnAbout(wxCommandEvent& WXUNUSED(event))
     info.SetDescription("wxTreeListCtrl wxWidgets sample.");
     info.SetCopyright("(C) 2011 Vadim Zeitlin <vadim@wxwidgets.org>");
 
-    wxAboutBox(info);
+    wxAboutBox(info, this);
 }
 
 void MyFrame::OnExit(wxCommandEvent& WXUNUSED(event))