Log Message:
gnutls: updated to 3.6.13

Version 3.6.13:

** libgnutls: Fix a DTLS-protocol regression (caused by TLS1.3 support), since 3.6.3.
   The DTLS client would not contribute any randomness to the DTLS negotiation,
   breaking the security guarantees of the DTLS protocol
   [GNUTLS-SA-2020-03-31, CVSS: high]

** libgnutls: Added new APIs to access KDF algorithms.

** libgnutls: Added new callback gnutls_keylog_func that enables a custom
   logging functionality.

** libgnutls: Added support for non-null terminated usernames in PSK
   negotiation.

** gnutls-cli-debug: Improved support for old servers that only support
   SSL 3.0.

** API and ABI modifications:
gnutls_hkdf_extract: Added
gnutls_hkdf_expand: Added
gnutls_pbkdf2: Added
gnutls_session_get_keylog_function: Added
gnutls_session_set_keylog_function: Added
gnutls_prf_hash_get: Added
gnutls_psk_server_get_username2: Added
gnutls_psk_set_client_credentials2: Added
gnutls_psk_set_client_credentials_function2: Added
gnutls_psk_set_server_credentials_function2: Added