xfree86: tell users to disable AutoAddDevices, not AllowEmptyInput.

Technically, disabling AEI is the right suggestion. AEI off forces the
server to init the built-in defaults for input devices (or pick the first
one from the config file). At the same time, hotplugging is still available
with AEI off.

Unfortunatly, in the vast majority of cases users want to simply disable
hotplugging or have a working server while the local HAL configuration is
broken or missing. Disabling AEI will lead to duplicate events, triple
keystrokes, etc. once the configuration works again.
It's not actually required to remove AEI once hotplugging works again,
though it will in many cases lead to a setup that appears broken.

Asking users to disable AutoAddDevices instead means those users disable
hotplugging, can then fix the HAL setup and they _must_ remove the config
line again to test if hotplugging works again. Which doesn't leave them with
a broken config once everything is working nice and dandy. Less bugreports,
everybody wins.

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
Acked-by: Dan Nicholson <dbn.lists@gmail.com>
Acked-by: Daniel Stone <daniel@fooishbar.org>
Acked-by: Rémi Cardona <remi@gentoo.org>
Acked-by: James Cloos <cloos@jhcloos.com>
(cherry picked from commit 761ae22f88)

hw/xfree86/common/xf86Config.c

@@ -1456,7 +1456,7 @@ checkCoreInputDevices(serverLayoutPtr servlayoutp, Bool implicitLayout)
 #ifdef CONFIG_HAL
 	xf86Msg(X_INFO, "The server relies on HAL to provide the list of "
 	                "input devices.\n\tIf no devices become available, "
-	                "reconfigure HAL or disable AllowEmptyInput.\n");
+	                "reconfigure HAL or disable AutoAddDevices.\n");
 #else
 	xf86Msg(X_INFO, "HAL is disabled and no input devices were configured.\n"
 			"\tTry disabling AllowEmptyInput.\n");