Plane: split out the tailsitter transition complete code

use both roll and pitch to trigger completion of transition. This
copes with situations where the plane has managed to get itself rolled
over far enough that it can't recover into hover

ArduPlane/quadplane.cpp

@@ -1043,7 +1043,7 @@ void QuadPlane::update_transition(void)
 
     if (is_tailsitter()) {
         if (transition_state == TRANSITION_ANGLE_WAIT &&
-            (ahrs_view->pitch_sensor < -tailsitter.transition_angle*100 || plane.fly_inverted())) {
+            tailsitter_transition_complete()) {
             GCS_MAVLINK::send_statustext_all(MAV_SEVERITY_INFO, "Transition done");
             transition_state = TRANSITION_DONE;
         }

ArduPlane/quadplane.h

@@ -83,6 +83,9 @@ public:
     
     // create outputs for tailsitters
     void tailsitter_output(void);
+
+    // check if we have completed transition
+    bool tailsitter_transition_complete(void);
     
     struct PACKED log_QControl_Tuning {
         LOG_PACKET_HEADER;

ArduPlane/tailsitter.cpp

@@ -44,3 +44,20 @@ void QuadPlane::tailsitter_output(void)
     }
 }
 
+
+/*
+  return true when we have completed enough of a transition to switch to fixed wing control
+ */
+bool QuadPlane::tailsitter_transition_complete(void)
+{
+    if (plane.fly_inverted()) {
+        // transition immediately
+        return true;
+    }
+    if (ahrs_view->pitch_sensor < -tailsitter.transition_angle*100 ||
+        ahrs_view->roll_sensor < -tailsitter.transition_angle*100) {
+        return true;
+    }
+    // still waiting
+    return false;
+}