SNI support rfc-6066

[brk0v]

Add SNI support rfc-6066.
Example of usage (you need need to implement tlsCtxStorage object):

// callback
func sniCallback(ssl *openssl.SSL) openssl.SSLTLSExtErr {
    host  := ssl.GetServername()

    if len(host) == 0 {
        return openssl.SSLTLSEXTErrNoAck
    }

    // check if we are already in default host
    if defaulHost, err := tlsCtxStorage.GetDefaultHost(); host == defaulHost && 
        err == nil {
            return openssl.SSLTLSExtErrOK
    }

    // get ctx
    ctx, err := tlsCtxStorage.GetCtx(host);
    if err != nil || ctx == nil {
        return openssl.SSLTLSEXTErrNoAck 
    }
    logger.Debugf("Changed context for: %s.", host)

    // set proper ctx
    ssl.SetSSLCtx(ctx)

    /*
    * SSL_set_SSL_CTX() only changes certs as of 1.0.0d
    * adjust other things we care about
    */

    ssl.SetVerify(ctx.VerifyMode(), ctx.GetVerifyCallback())
    ssl.SetVerifyDepth(ctx.GetVerifyDepth())

    ssl.ClearOptions(ssl.GetOptions() &^ ctx.GetOptions())
    ssl.SetOptions(ctx.GetOptions())

    return openssl.SSLTLSExtErrOK 
}

[jtolio]

so actually, before i review more, would you mind squashing these commits into one and rebasing?

[jtolio]

this has moved to #17