Avoid warning:

../../../../ext/fox16_c/FXRbApp.cpp: In static member function ‘static FXRbApp* FXRbApp::constructAndInit(const FXchar*, const FXchar*)’:
../../../../ext/fox16_c/FXRbApp.cpp:58:28: warning: deprecated conversion from string constant to ‘char*’ [-Wwrite-strings]
   static char* argv[]={"",0};
                            ^