Copter: add gripper release FS_Option

ArduCopter/Copter.h

@@ -607,6 +607,7 @@ private:
         RC_CONTINUE_IF_GUIDED           = (1<<2),   // 4
         CONTINUE_IF_LANDING             = (1<<3),   // 8
         GCS_CONTINUE_IF_PILOT_CONTROL   = (1<<4),   // 16
+        RELEASE_GRIPPER                 = (1<<5),   // 32
     };
 
     static constexpr int8_t _failsafe_priorities[] = {

ArduCopter/Parameters.cpp

@@ -951,7 +951,7 @@ const AP_Param::GroupInfo ParametersG2::var_info[] = {
     // @DisplayName: Failsafe options bitmask
     // @Description: Bitmask of additional options for battery, radio, & GCS failsafes. 0 (default) disables all options.
     // @Values: 0:Disabled, 1:Continue if in Auto on RC failsafe only, 2:Continue if in Auto on GCS failsafe only, 3:Continue if in Auto on RC and/or GCS failsafe, 4:Continue if in Guided on RC failsafe only, 8:Continue if landing on any failsafe, 16:Continue if in pilot controlled modes on GCS failsafe, 19:Continue if in Auto on RC and/or GCS failsafe and continue if in pilot controlled modes on GCS failsafe
-    // @Bitmask: 0:Continue if in Auto on RC failsafe, 1:Continue if in Auto on GCS failsafe, 2:Continue if in Guided on RC failsafe, 3:Continue if landing on any failsafe, 4:Continue if in pilot controlled modes on GCS failsafe
+    // @Bitmask: 0:Continue if in Auto on RC failsafe, 1:Continue if in Auto on GCS failsafe, 2:Continue if in Guided on RC failsafe, 3:Continue if landing on any failsafe, 4:Continue if in pilot controlled modes on GCS failsafe, 5:Release Gripper
     // @User: Advanced
     AP_GROUPINFO("FS_OPTIONS", 36, ParametersG2, fs_options, 0),
 

ArduCopter/events.cpp

@@ -378,5 +378,11 @@ void Copter::do_failsafe_action(Failsafe_Action action, ModeReason reason){
             arming.disarm(AP_Arming::Method::FAILSAFE_ACTION_TERMINATE);
 #endif
     }
+
+#if GRIPPER_ENABLED == ENABLED
+    if (failsafe_option(FailsafeOption::RELEASE_GRIPPER)) {
+        copter.g2.gripper.release();
+    }
+#endif
 }