Fix handling of CURLOPT_CAINFO and CURLOPT_CAPATH

[DennisHeimbigner]

re: Issue Unidata/netcdf4-python#1246

This provides a partial solution to the above PR.
The underlying problem is with libcurl, but at least a
workaround should be possible by creating a "~/.ncrc" file
containing the line "HTTP.SSL_CAINFO=<path to the cert (.crt) file>".
This was not working for obscure reasons. This PR should fix it.

Misc. Other Changes

• Update/fix configure.ac to properly test for libcurl version >= 7.66.0
• Update include/netcdf_json.h
• Remove use of strlcat from plugins.
• Fix applicability of .rc file entries

[jswhit]

Thanks @DennisHeimbigner for fixing this! Would it be possible to add a netcdf API function for setting the cert path programatically? That way the python package could use certifi to determine the location of the cert files and set the path on import, without requiring any action by the user. This is what was done in the PROJ C lib (OSGeo/PROJ#2320) when a similar problem was encountered in the python interface.

[DennisHeimbigner]

I think you can already do this. The netcdf.h API includes the following function:

/* Programmatic access to the internal .rc table /
...
/ Set/overwrite the value corresponding to key /
EXTERNL int nc_rc_set(const char key, const char* value);

You should be able to call "nc_rc_set("HTTP.SSL.CAINFO",<path to .crt file>)
You just need to make sure you do this before you do any other actions.

[jswhit]

it would be nice to get this merged soon so I can build new netcdf4-python wheels that work with https URLs