Give AP_GPS_None a ctor so that it fits in.

git-svn-id: https://arducopter.googlecode.com/svn/trunk@1247 f9c3cf11-9bcb-44bc-f272-b75c42450872

libraries/AP_GPS/AP_GPS_None.h

@@ -7,6 +7,8 @@
 
 class AP_GPS_None : public GPS
 {
+public:
+	AP_GPS_None(Stream *s) : GPS(s) {}
 	virtual void init(void) {};
 	virtual bool read(void) { return false; };
 };