v4l grabber wont crash hyperiond anymore (#168)

* v4l errors won't lead to crash hyperiond (exceptions are catched)
v4l auto device mode with better log messages
createV4l in hyperiond.cpp refactored, now v4l is always available as long as it is compiled in

* change back, code accidently altered

* fix compile of dispmanx grabber

include/grabber/DispmanxWrapper.h

@@ -62,8 +62,6 @@ private:
 	const int _updateInterval_ms;
 	/// The timeout of the led colors [ms]
 	const int _timeout_ms;
-	/// The priority of the led colors
-	const int _priority;
 
 	/// The image used for grabbing frames
 	Image<ColorRgba> _image;

include/grabber/V4L2Grabber.h

@@ -57,6 +57,7 @@ public slots:
 
 signals:
 	void newFrame(const Image<ColorRgb> & image);
+	void readError(const char* err);
 
 private slots:
 	int read_frame();
@@ -135,4 +136,5 @@ private:
 	
 	Logger * _log;
 	bool _initialized;
+	bool _deviceAutoDiscoverEnabled;
 };

include/grabber/V4L2Wrapper.h

@@ -44,6 +44,7 @@ public slots:
 
 private slots:
 	void newFrame(const Image<ColorRgb> & image);
+	void readError(const char* err);
 
 	virtual void action();
 	void checkSources();