CURLINFO_TLS_SESSION.3: clarify TLS library support before 7.48.0

docs/libcurl/opts/CURLINFO_TLS_SESSION.3

@@ -51,7 +51,8 @@ All TLS-based
 .SH EXAMPLE
 TODO
 .SH AVAILABILITY
-Added in 7.34.0
+Added in 7.34.0, and supported OpenSSL, GnuTLS, NSS and gskit only up until
+7.48.0 was released.
 .SH RETURN VALUE
 Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
 .SH "SEE ALSO"