Allow setting enabled TLS versions in Sofia-SIP

Previously if the TPTAG_TLS_VERSION was set to a non-zero value we
supported only TLSv1 (but not TLSv1.1 or TLSv1.2), and if was set to
zero we supported all versions of TLS and SSL (including the
ridiculous SSLv2).

Now we take an integer field where various bits can be set indicating
which versions of TLS we would like to support.
Support setting enabled TLS versions in mod_sofia

Previously if tls-version was set to tlsv1 we supported only TLSv1,
but if it was set to sslv23 we supported all versions of TLS.  This
was a weird incorrectly documented behavior that we hope no one was
relying on.

Now we can pass a comma-separated list of TLS/SSL versions that we
would like to support in tls-version.

FS-5839 --resolve