Function gio_sys::g_proxy_connect_async

pub unsafe extern "C" fn g_proxy_connect_async(
    proxy: *mut GProxy, 
    connection: *mut GIOStream, 
    proxy_address: *mut GProxyAddress, 
    cancellable: *mut GCancellable, 
    callback: GAsyncReadyCallback, 
    user_data: gpointer
)