Add GetNativeHandle() to wxWebSession and wxWebRequest

This allows to retrieve the handles used internally in order to do
something not supported by the public API yet.

include/wx/private/webrequest_curl.h

@@ -64,6 +64,11 @@ public:
 
     CURL* GetHandle() const { return m_handle; }
 
+    wxWebRequestHandle GetNativeHandle() const wxOVERRIDE
+    {
+        return (wxWebRequestHandle)GetHandle();
+    }
+
     bool StartRequest();
 
     void HandleCompletion();
@@ -133,6 +138,11 @@ public:
 
     wxVersionInfo GetLibraryVersionInfo() wxOVERRIDE;
 
+    wxWebSessionHandle GetNativeHandle() const wxOVERRIDE
+    {
+        return (wxWebSessionHandle)m_handle;
+    }
+
     bool StartRequest(wxWebRequestCURL& request);
 
     void CancelRequest(wxWebRequestCURL* request);