AP_LandingGear: standardize inclusion of libaries headers

This commit changes the way libraries headers are included in source files:

 - If the header is in the same directory the source belongs to, so the
 notation '#include ""' is used with the path relative to the directory
 containing the source.

 - If the header is outside the directory containing the source, then we use
 the notation '#include <>' with the path relative to libraries folder.

Some of the advantages of such approach:

 - Only one search path for libraries headers.

 - OSs like Windows may have a better lookup time.

libraries/AP_LandingGear/AP_LandingGear.cpp

@@ -1,10 +1,10 @@
 // -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-
 
-#include <AP_LandingGear.h>
-#include <AP_Relay.h>
-#include <AP_Math.h>
-#include <RC_Channel.h>
-#include <AP_HAL.h>
+#include "AP_LandingGear.h"
+#include <AP_Relay/AP_Relay.h>
+#include <AP_Math/AP_Math.h>
+#include <RC_Channel/RC_Channel.h>
+#include <AP_HAL/AP_HAL.h>
 
 extern const AP_HAL::HAL& hal;
 

libraries/AP_LandingGear/AP_LandingGear.h

@@ -6,8 +6,8 @@
 #ifndef AP_LANDINGGEAR_H
 #define AP_LANDINGGEAR_H
 
-#include <AP_Param.h>
-#include <AP_Common.h>
+#include <AP_Param/AP_Param.h>
+#include <AP_Common/AP_Common.h>
 
 #define AP_LANDINGGEAR_SERVO_RETRACT_PWM_DEFAULT    1250    // default PWM value to move servo to when landing gear is up
 #define AP_LANDINGGEAR_SERVO_DEPLOY_PWM_DEFAULT     1750    // default PWM value to move servo to when landing gear is down