astro/gpsd: Update to 3.20
- Update to 3.20 (welcome ubxtool and gpsrinex!)
- Fix SConstruct per python3 [1]
- Replace spaces by tabs (pet portlint)
Changelog: - https://gitlab.com/gpsd/gpsd/-/blob/master/NEWS#L16
[1] scons is py27 only and check py27 packages for a py37 port. I commented these tests in SConstruct since we already do it in our Makefile.