ntp: add client support for network correction

If the network correction is known for both the request and response,
and their sum is not larger that the measured peer delay, allowing the
transparent clocks to be running up to 100 ppm faster than the client's
clock, apply the corrections to the NTP offset and peer delay. Don't
correct the root delay to not change the estimated maximum error.

cmdparse.c

@@ -118,6 +118,9 @@ CPS_ParseNTPSourceAdd(char *line, CPS_NTP_Source *src)
         case NTP_EF_EXP_MONO_ROOT:
           src->params.ext_fields |= NTP_EF_FLAG_EXP_MONO_ROOT;
           break;
+        case NTP_EF_EXP_NET_CORRECTION:
+          src->params.ext_fields |= NTP_EF_FLAG_EXP_NET_CORRECTION;
+          break;
         default:
           return 0;
       }