Since 7.54 --tlsv1. options use the specified version or later, however
older versions of curl documented it as using just the specified version
which may or may not have happened depending on the TLS library.
Document this discrepancy to allay confusion for users familiar with the
old documentation that expect just the specified version.
Fixes https://github.com/curl/curl/issues/4097
Closes https://github.com/curl/curl/pull/4119
The code treated the set version as the *exact* version to require in
the TLS handshake, which is not what other TLS backends do and probably
not what most people expect either.
Reported-by: Andreas Olsson
Assisted-by: Gaurav Malhotra
Fixes#2691Closes#2694
