Cover a case of not adding needless trailing / while accessing a backend from
top level of the URL.

As / are stripped while parsing the url, expose the situation that even if
url ends with a /, it won't be sent for top level access.

Here is the mapping of configured URL, path accessed on the CDN side and path
sent to the backend:

 * backend/index.html   frontend/     index.html
 * backend/index.html   frontend/a    index.html/a
 * backend/index.html   frontend/a/   index.html/a/
 * backend/index.html/  frontend/     index.html
 * backend/index.html/  frontend/a    index.html/a
 * backend/index.html/  frontend/a/   index.html/a/

The new ghostscript could not decrypt some password protected files. It turned out to be a bug in ghostscript but in the process of investigating I thought it might be related to missing libidn that is also used in PDF passwords, so I added it.

See merge request nexedi/slapos!1455

Fixes decryption of some password protected PDFs

INFO configure: WARNING: unrecognized options: --disable-threadsafe

without libidn, decrypting password protected PDFs does not fully work.

This is a fixup of f6281e7a.

This fixes 3c514224

Since nginx 1.25.1 ssl directive has been dropped, so fix the configuration
template to work with 1.25.2.

Update nginx-push-stream to follow nginx API changes.

Will support zlib 1.3+

Extend PATH to make xzcat available.

Extend PATH to make xzcat available.

Enforce python3 usage, as the newer version requires python3.

Empty values are considered not provided, so provide a template which
produces a file with a lone comment.

Instead of using openssl-1.0 and overriding the new versions to use
openssl, use openssl by default and override in the old versions to use
openssl-1.0