Share the PX4IO protocol header, such as it is, between the two apps.

Stop using systemlib in the PX4IO firmware; it has expectations that can't reasonably be met.

nuttx/configs/px4io/io/appconfig

@@ -1,8 +1,6 @@
 ############################################################################
-# configs/stm3210e-eval/nsh/appconfig
 #
-#   Copyright (C) 2011-2012 Gregory Nutt. All rights reserved.
-#   Author: Gregory Nutt <gnutt@nuttx.org>
+#   Copyright (C) 2012 PX4 Development Team. All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions
@@ -14,7 +12,7 @@
 #    notice, this list of conditions and the following disclaimer in
 #    the documentation and/or other materials provided with the
 #    distribution.
-# 3. Neither the name NuttX nor the names of its contributors may be
+# 3. Neither the name PX4 nor the names of its contributors may be
 #    used to endorse or promote products derived from this software
 #    without specific prior written permission.
 #
@@ -33,7 +31,4 @@
 #
 ############################################################################
 
-# Path to px4io app containing the user_start entry point
-
 CONFIGURED_APPS += px4io
-CONFIGURED_APPS += systemlib