[PROJ] Suggestion - add EPSG version to proj_info()

[Roger Bivand]

I realise that simple SQL on proj.db can return the EPSG.VERSION key from 
the metadata table in proj.db, and that PROJ and EPSG versions are 
hard-wired in a single run-time. Could also the built-time EPSG version be 
made available?

In https://github.com/rsbivand/rgrass7/issues/27, two Windows binaries, 
each built against PROJ, but different versions, one EPSG 9 and one EPSG 
10, so that when one (rgdal) resets PROJ_LIB to EPSG 10, GRASS fails to 
read proj.db because it is EPSG 10, with g.proj -w returning an error.

An alternative would be a mechanism to allow rgdal to use "its" PROJ 
search path, and GRASS (or other binary software) to use "its" search 
path, but while I implemented this for PROJ 6 in rgdal, I went back to 
PROJ_LIB because we need both the proj.db directory and the CDN download 
directory (on both sides, I expect).

The problem only affects stand-alone binary distributions without an 
underlying package manager to ensure harmonisation across installed 
software.

Interested in views, I've raised this on grass-dev too, but I think that 
it is more general, hence post here.

Best wishes,

Roger

-- 
Roger Bivand
Emeritus Professor
Department of Economics, Norwegian School of Economics,
Postboks 3490 Ytre Sandviken, 5045 Bergen, Norway.
e-mail: Roger.Bivand at nhh.no
https://orcid.org/0000-0003-2392-6140
https://scholar.google.no/citations?user=AWeghB0AAAAJ&hl=en