Update to 1.3.6c
    
    - New upstream release 1.3.6c
      - Use-after-free vulnerability in memory pools during data transfer
        (https://github.com/proftpd/proftpd/issues/903)
      - Fix mod_tls compilation with LibreSSL 2.9.x
        (https://github.com/proftpd/proftpd/issues/810)
      - MaxClientsPerUser was not enforced for SFTP logins when mod_digest was
        enabled (https://github.com/proftpd/proftpd/issues/750)
      - mod_sftp now handles an OpenSSH-specific private key format; it detects
        such keys, and logs a hint about reformatting them to a supported format
        (https://github.com/proftpd/proftpd/issues/793)
      - Directory listing was slower compared to previous ProFTPD versions
        (https://github.com/proftpd/proftpd/issues/793)
      - mod_sftp crashed when using pubkey-auth with DSA keys
        (https://github.com/proftpd/proftpd/issues/866)
      - Fix improper handling of TLS CRL lookups (CVE-2019-19269, CVE-2019-19270,
        https://github.com/proftpd/proftpd/issues/859)
      - Leaking PAM handler and data in case of unsuccessful authentication
        (https://github.com/proftpd/proftpd/issues/870)
      - SSH authentication failed for many clients due to receiving of
        SSH_MSG_IGNORE packet (http://bugs.proftpd.org/show_bug.cgi?id=4385)
      - SFTP publickey authentication failed unexpectedly when user had no shadow
        password info. (https://github.com/proftpd/proftpd/issues/890)
      - ftpasswd failed to restore password file permissions in some cases
        (https://github.com/proftpd/proftpd/issues/898)
      - Out-of-bounds read in mod_cap getstateflags() function; this has been
        addressed by updating the bundled version of libcap
        (https://github.com/proftpd/proftpd/issues/902)
        Note that this build of ProFTPD uses the system version of libcap and not
        the bundled version