Added room in land_detector code for free-fall detection

src/modules/land_detector/land_detector_main.cpp

@@ -55,6 +55,9 @@
 #include "MulticopterLandDetector.h"
 #include "VtolLandDetector.h"
 
+namespace landdetection
+{
+
 //Function prototypes
 static int land_detector_start(const char *mode);
 static void land_detector_stop();
@@ -208,3 +211,5 @@ exiterr:
 	PX4_WARN("mode can either be 'fixedwing' or 'multicopter'");
 	return 1;
 }
+
+}