Merge branch 'maint-0.2.8' into maint-0.2.9

  o Major bugfixes (relay, crash, assertion failure):

    - Fix a timing-based assertion failure that could occur when the

      circuit out-of-memory handler freed a connection's output buffer.

      Fixes bug 23690; bugfix on 0.2.6.1-alpha.

  if (conn->outbuf) {

    result += buf_allocation(conn->outbuf);

    buf_clear(conn->outbuf);

    conn->outbuf_flushlen = 0;

  }

  if (conn->type == CONN_TYPE_DIR) {

    dir_connection_t *dir_conn = TO_DIR_CONN(conn);