Copter: use fabsf() instead of labs()

wrap_180_cd returns a float

substracting a float from an int32 returns a float

ArduCopter/mode_auto.cpp

@@ -1748,7 +1748,7 @@ bool Copter::ModeAuto::verify_yaw()
     }
 
     // check if we are within 2 degrees of the target heading
-    return (labs(wrap_180_cd(ahrs.yaw_sensor-auto_yaw.yaw())) <= 200);
+    return (fabsf(wrap_180_cd(ahrs.yaw_sensor-auto_yaw.yaw())) <= 200);
 }
 
 // verify_nav_wp - check if we have reached the next way point

ArduCopter/mode_autotune.cpp

@@ -431,18 +431,18 @@ bool Copter::ModeAutoTune::check_level(const LEVEL_ISSUE issue, const float curr
 bool Copter::ModeAutoTune::currently_level()
 {
     if (!check_level(LEVEL_ISSUE_ANGLE_ROLL,
-                     labs(ahrs.roll_sensor - roll_cd),
+                     fabsf(ahrs.roll_sensor - roll_cd),
                      AUTOTUNE_LEVEL_ANGLE_CD)) {
         return false;
     }
 
     if (!check_level(LEVEL_ISSUE_ANGLE_PITCH,
-                     labs(ahrs.pitch_sensor - pitch_cd),
+                     fabsf(ahrs.pitch_sensor - pitch_cd),
                      AUTOTUNE_LEVEL_ANGLE_CD)) {
         return false;
     }
     if (!check_level(LEVEL_ISSUE_ANGLE_YAW,
-                     labs(wrap_180_cd(ahrs.yaw_sensor-(int32_t)desired_yaw)),
+                     fabsf(wrap_180_cd(ahrs.yaw_sensor-(int32_t)desired_yaw)),
                      AUTOTUNE_LEVEL_ANGLE_CD)) {
         return false;
     }

ArduCopter/mode_rtl.cpp

@@ -227,7 +227,7 @@ void Copter::ModeRTL::loiterathome_run()
     if ((millis() - _loiter_start_time) >= (uint32_t)g.rtl_loiter_time.get()) {
         if (auto_yaw.mode() == AUTO_YAW_RESETTOARMEDYAW) {
             // check if heading is within 2 degrees of heading when vehicle was armed
-            if (labs(wrap_180_cd(ahrs.yaw_sensor-copter.initial_armed_bearing)) <= 200) {
+            if (fabsf(wrap_180_cd(ahrs.yaw_sensor-copter.initial_armed_bearing)) <= 200) {
                 _state_complete = true;
             }
         } else {