pps_capture: implementation of pulse per second capture driver

msg/CMakeLists.txt

@@ -118,6 +118,7 @@ set(msg_files
 	orbit_status.msg
 	parameter_update.msg
 	ping.msg
+	pps_capture.msg
 	position_controller_landing_status.msg
 	position_controller_status.msg
 	position_setpoint.msg

msg/pps_capture.msg

@@ -0,0 +1,3 @@
+uint64 timestamp			# time since system start (microseconds)
+uint64 rtc_timestamp		# captured time in microseconds from real-time clock at PPS event
+int32 rtc_drift_time		# time drift between RTC and PPS event in microseconds