They serve very little purpose and mostly just add noise. Most of them
have been around for a very long time. I read them all before removing
or rephrasing them.

Ref: #3876
Closes #3883

Currently you can do things like --cert <(cat ./cert.crt) with (at least) the
openssl backend, but that doesn't work for nss because is_file rejects fifos.

I don't actually know if this is sufficient, nss might do things internally
(like seeking back) that make this not work, so actual testing is needed.

Closes #3807

As soon as a TLS backend gets ALPN conformation about the specific HTTP
version it can now set the multiplex situation for the "bundle" and
trigger moving potentially queued up transfers to the CONNECT state.

Closes #3808

Use descriptive text strings rather than decimal numbers.

NSS may be built without support for the latest SSL/TLS versions,
leading to "SSL version range is not valid" errors when the library
code supports a recent version (e.g. TLS v1.3) but it has explicitly
been disabled.

This change adjusts the maximum SSL version requested by libcurl to
be the maximum supported version at runtime, as long as that version
is at least as high as the minimum version required by libcurl.

Fixes #3261

The function does not return the same value as snprintf() normally does,
so readers may be mislead into thinking the code works differently than
it actually does. A different function name makes this easier to detect.

Reported-by: Tomas Hoger
Assisted-by: Daniel Gustafsson
Fixes #3296
Closes #3297

Closes #3291

Closes #3262