Silence some uncontroversial warnings

https://bugzilla.gnome.org/show_bug.cgi?id=711547

gio/gresolver.c

@@ -294,7 +294,9 @@ handle_ip_address (const char  *hostname,
                    GError     **error)
 {
   GInetAddress *addr;
+#ifndef G_OS_WIN32
   struct in_addr ip4addr;
+#endif
 
   addr = g_inet_address_new_from_string (hostname);
   if (addr)

glib/gmain.c

@@ -4012,6 +4012,7 @@ g_main_context_poll (GMainContext *context,
   if (n_fds || timeout != 0)
     {
 #ifdef	G_MAIN_POLL_DEBUG
+      poll_timer = NULL;
       if (_g_main_poll_debug)
 	{
 	  g_print ("polling context=%p n=%d timeout=%d\n",

glib/gutils.c

@@ -1797,6 +1797,7 @@ g_win32_get_system_data_dirs_for_module (void (*address_of_function)(void))
   gchar *p;
   gchar *exe_root;
 
+  hmodule = NULL;
   if (address_of_function)
     {
       G_LOCK (g_utils_global);