RC_Channel: Allow a RC_OVERRIDE_TIMEOUT of -1 to use the overrides

forever

libraries/RC_Channel/RC_Channel.cpp

@@ -327,7 +327,9 @@ void RC_Channel::clear_override()
 
 bool RC_Channel::has_override() const
 {
-    return (override_value > 0) && ((AP_HAL::millis() - last_override_time) < *RC_Channels::override_timeout * 1000);
+    int32_t override_timeout = (int32_t)(*RC_Channels::override_timeout);
+    return (override_value > 0) && ((override_timeout < 0) ||
+                                    ((AP_HAL::millis() - last_override_time) < (uint32_t)(override_timeout * 1000)));
 }
 
 bool RC_Channel::min_max_configured() const

libraries/RC_Channel/RC_Channels.cpp

@@ -99,7 +99,7 @@ const AP_Param::GroupInfo RC_Channels::var_info[] = {
 
     // @Param: _OVERRIDE_TIME
     // @DisplayName: RC override timeout
-    // @Description: Timeout after which RC overrides will no longer be used, and RC input will resume, 0 will disable RC overrides
+    // @Description: Timeout after which RC overrides will no longer be used, and RC input will resume, 0 will disable RC overrides, -1 will never timeout, and continue using overrides until they are disabled
     // @User: Advanced
     // @Range: 0.0 120.0
     // @Units: s