Log Message:
geography/gpsd: Update to 3.20

3.20: 2019-12-31
  Change README into an asciidoc file and publish HTML from it
  Add NED and geoid_sep to gps_fix_t and TPV JSON.
  Add "-e NED" to ubxtool to enable NED messages.
  gpsdata.separation replaced by gpsdata.fix.geoid_sep.
  Remove nofloats build option.
  TPV JSON "alt" is now fixed at WGS84.  Probably.
  xgps now uses XGPSOPTS environment variable.
  add health variable to satellite_t
  change satellite_t elevation and azimuth to double
  satellite_t elevation, azimuth, and ss use NAN for unknown value.
  add altMSL, altHAE, and depth, to gps_fix_t
  altitude in gps_fix_t is deprecated and undefined
  wgs84_separation() now return EGM2008 computed from 5x5 degree base data.
     The best results are close to cm, the worst off up to 12m.
  Move mag_var from gps_device_t to magnetic_var gps_data_t.
  Added mag_var() to interpolate magnetic variation (deviation) from a table.
  Remove true2magnetic() as mag_var() improves on it.
  Remove TIMEHINT_ENABLE.  It only worked when enabled.
  Remove NTP_ENABLE and NTPSHM_ENABLE.  It only worked when enabled.
  Remove PPS_ENABLE and TIMING_ENABLE.
  Add dgps_age and dgps_station to gps_fix_t
  Convert all timestamp_t to timespec_t.
  Remove FIXED_PORT_SPEED and FIXED_STOP_BITS build options.
  Add -s [speed] and -f [framing] runtime options to gpsd.
  A working CC and termios.h are mandatory.
  use the current leap second to determine the current GPS epoch.
  leapfetch.py, leapseconds.cache, timebase.h and leapfetch option gone.
  See also change histories in gps.h and gpsd.h