AC_PrecLand: replace header guard with pragma once

libraries/AC_PrecLand/AC_PrecLand.h

@@ -1,6 +1,5 @@
 /// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-
-#ifndef __AC_PRECLAND_H__
-#define __AC_PRECLAND_H__
+#pragma once
 
 #include <AP_Common/AP_Common.h>
 #include <AP_Math/AP_Math.h>
@@ -108,4 +107,3 @@ private:
     } _backend_state;
     AC_PrecLand_Backend         *_backend;  // pointers to backend precision landing driver
 };
-#endif	// __AC_PRECLAND_H__

libraries/AC_PrecLand/AC_PrecLand_Backend.h

@@ -1,6 +1,5 @@
 /// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-
-#ifndef __AC_PRECLAND_BACKEND_H__
-#define __AC_PRECLAND_BACKEND_H__
+#pragma once
 
 #include <AP_Common/AP_Common.h>
 #include <AP_Math/AP_Math.h>
@@ -43,4 +42,3 @@ protected:
     const AC_PrecLand&  _frontend;          // reference to precision landing front end
     AC_PrecLand::precland_state &_state;    // reference to this instances state
 };
-#endif	// __AC_PRECLAND_BACKEND_H__

libraries/AC_PrecLand/AC_PrecLand_Companion.h

@@ -1,6 +1,5 @@
 /// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-
-#ifndef __AC_PRECLAND_COMPANION_H__
-#define __AC_PRECLAND_COMPANION_H__
+#pragma once
 
 #include <AP_Common/AP_Common.h>
 #include <AP_Math/AP_Math.h>
@@ -45,4 +44,3 @@ private:
     uint64_t            _timestamp_us;          // timestamp when the image was captured(synced via UAVCAN)
     bool                _new_estimate;          // true if new data from the camera has been received
 };
-#endif	// __AC_PRECLAND_COMPANION_H__

libraries/AC_PrecLand/AC_PrecLand_IRLock.h

@@ -1,6 +1,5 @@
 /// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-
-#ifndef __AC_PRECLAND_IRLOCK_H__
-#define __AC_PRECLAND_IRLOCK_H__
+#pragma once
 
 #include <AP_Common/AP_Common.h>
 #include <AP_Math/AP_Math.h>
@@ -45,4 +44,3 @@ private:
 
 };
 #endif
-#endif	// __AC_PRECLAND_IRLOCK_H__