[Pound Mailing List] X-SSL-cipher header reports TLS connections as SSLv3

# Steps to reproduce
1. Copy the attached `pound.cfg` to `/etc/pound/`
2. Copy the attached `pound-test-cert.pem` to `/etc/ssl/private/`
3. Open a TCP port on port 8080: `netcat -t -l -p 8080`
4. `service pound start`
5. Make a TLS (not SSL!) request: `curl --tlsv1 --ciphers 'AES128-SHA'
-k https://127.0.0.1:8443/`
6. Look at the stdout of netcat, and see the value of HTTP request
header X-SSL-cipher that pound has injected into the request

## Expected
The connection is reported to be TLS

## Actual
The connection is reported to be SSLv3: "AES128-SHA SSLv3 Kx=RSA Au=RSA
Enc=AES(128) Mac=SHA1"

Wireshark debugging confirms that the curl connection is indeed a TLS
connection, rather than a SSLv3 connection.

# Impact
When trying to determine the impact of disabling SSLv3 (re POODLE), we
searched
our logs for how many clients used SSLv3, and this bug caused us to
believe we
had more SSLv3 traffic than we actually did.

# Why this is reported to be SSLv3
Looking into the pound code[0], X-SSL-cipher is populated with the
result of SSL_CIPHER_description().
In SSL_CIPHER_description() "The TLSv1.0 ciphers are flagged with
SSLv3."[1].
The AES ciphers are TLSv1 ciphers, and hence are reported as SSLv3 by
pound/openssl.

# Proposed fix
Add a X-SSL-version header, using SSL_get_version()[2]. I can produce a
patch for this, if it is considered an acceptable change.

I originally raised this against Ubuntu's bug tracker[3], but have since
found this mailing list, so am posting it here.

0.
https://github.com/mandiant/pound/blob/a3705bc06e44ec4a229fd38760d6c04c43ced6b6/http.c#L943
1. https://www.openssl.org/docs/ssl/SSL_CIPHER_get_name.html
2. https://www.openssl.org/docs/ssl/SSL_get_version.html
3. https://bugs.launchpad.net/ubuntu/+source/pound/+bug/1398007

-- 
Tom Fitzhenry