changes for error-free compile with wxWidgets 2.9.0

clientgui/AsyncRPC.cpp

clientgui/BOINCGUIApp.cpp

clientgui/BOINCListCtrl.cpp

clientgui/MainDocument.cpp

clientgui/ProjectListCtrl.cpp

clientgui/ProjectProcessingPage.cpp

clientgui/SkinManager.cpp

clientgui/ValidateURL.cpp

clientgui/common/wxFlatNotebook.cpp

clientgui/common/wxFlatNotebookImages.h

clientgui/res/multicore.xpm

clientgui/sg_CustomControls.cpp