gpsd struct no longer has an epe field

[lukehutch]

After updating gpsd recently, I got the following compile error in gps_umd/gpsd_client:

/home/luke/catkin_ws/src/gps_umd/gpsd_client/src/client.cpp: In member function ‘void GPSDClient::process_data_gps(gps_data_t*)’:
/home/luke/catkin_ws/src/gps_umd/gpsd_client/src/client.cpp:178:22: error: ‘struct gps_data_t’ has no member named ‘epe’
  178 |         fix.err = p->epe;
      |                      ^~~

Version: Fedora gpsd-devel-3.19-2.fc31.x86_64

[lukehutch]

From the header gps.h:

 * 8.0 - Change shape of rawdata_t.
 *       Remove epe from gps_data_t, it duplicates gps_fix_t eph
 *       Added sep (estimated spherical error, 3D)
 *       Note: Some GPS call eph as epe, others call sep as epe
 *       Add gps_fix_t datum string, and qErr