postgis: cleanup
Another part of https://github.com/NixOS/nixpkgs/pull/38698, though I did cleanup even more.
Moving docs to separate output should save another 30MB.
I did pin poppler to 0.61 just to be sure GDAL doesn't break again next
time poppler changes internal APIs.
Add postgis 2.4.0
doesn't remove v2.3.1. There are some big change in 2.4 that people may
don't want. see https://postgis.net/docs/release_notes.html#idm41021
fix test call
modify following recommandation of lsix
Fixes#15512 and #16032
With the multi output, postgresql cannot find at runtime what is its
basedir when looking for libdir and pkglibdir. This commit fixes that.