AP_SpdHgtControl: sync TECS with plane4.0

libraries/AP_SpdHgtControl/AP_SpdHgtControl.h

@@ -63,6 +63,9 @@ public:
 	// set path_proportion accessor
     virtual void set_path_proportion(float path_proportion) = 0;
 
+    // reset on next loop
+    virtual void reset(void) = 0;
+
 	// add new controllers to this enum. Users can then
 	// select which controller to use by setting the
 	// SPDHGT_CONTROLLER parameter