msg: Add GPS check status to estimator_status uORB topic

msg/estimator_status.msg

@@ -5,3 +5,14 @@ uint8 nan_flags			# Bitmask to indicate NaN states
 uint8 health_flags		# Bitmask to indicate sensor health states (vel, pos, hgt)
 uint8 timeout_flags		# Bitmask to indicate timeout flags (vel, pos, hgt)
 float32[28] covariances	# Diagonal Elements of Covariance Matrix
+uint16 gps_check_fail_flags     # Bitmask to indicate status of GPS checks - see definition below
+# bits are true when corresponding test has failed
+# 0 : minimum required sat count fail
+# 1 : minimum required GDoP fail
+# 2 : maximum allowed horizontal position error fail
+# 3 : maximum allowed vertical position error fail
+# 4 : maximum allowed speed error fail
+# 5 : maximum allowed horizontal position drift fail
+# 6 : maximum allowed vertical position drift fail
+# 7 : maximum allowed horizontal speed fail
+# 8 : maximum allowed vertical velocity discrepancy fail