[common.xml] MAV_PROTOCOL_CAPABILITY_PARAM_ENCODE_C_CAST flag missing

The common.xml is out of date, it is missing autopilot capability MAV_PROTOCOL_CAPABILITY_PARAM_ENCODE_C_CAST .

https://github.com/mavlink/mavlink/blob/master/message_definitions/v1.0/common.xml#L3235

I was about to fix deprecation of MAV_PROTOCOL_CAPABILITY_PARAM_FLOAT by using MAV_PROTOCOL_CAPABILITY_PARAM_ENCODE_C_CAST instead in GCS_Mavlink and found this issue.