gnunet: update to version 0.20.0

gnunet: update to version 0.20.0

v0.20.0:
  - GNUNET_TESTING_get_testname_from_underscore renamed to GNUNET_STRINGS_get_suffix_from_binary_name and moved from libgnunettesting to libgnuneutil
  - Move GNUNET_s into libgnunetutil.
  - re-introduce compiler annotation for array size in signature
  - function-signature adjustment due to compiler error
  - GNUNET_PQ_get_oid removed, GNUNET_PQ_get_oid_by_name improved
  - Added GNUNET_PQ_get_oid_by_name
  - added GNUNET_PQ_get_oid()
  - Added new CCA-secure KEM and use in IDENTITY encryption
  - Add KEM API to avoid ephemeral private key management
  - Add new GNUNET_PQ_event_do_poll() API to gnunet_pq_lib.h
  - Added API to support arrays in query results
  - Improve PQ API documentation.
  - API for array types extended for times
  - API extended for array query types
  - relevant array-types in queries (not results) in postgresql added
  - just style fixes, int to enum
  - initial steps towards support of array-types in posgresql
  - adds GNUNET_JSON_spec_object_const() and GNUNET_JSON_spec_array_const()

Signed-off-by: Daniel Golle <daniel@makrotopia.org>