gnunet: update to version 0.25.1

gnunet: update to version 0.25.1

GNUnet 0.25 dropped the autotools based build system and now requires
being built with Meson. As expected there are some cross-compiling
related issues which have been fixed using downstream patches by now.

v0.25.1:
  - transport: hotfix incorrect communicator key derivations
  - tests: make failing tests work again
  - util: Change to assigned HPKE codepoint for DHKEM+Elligator. See https://www.iana.org/assignments/hpke/
  - fs: service failed to start because of PILS addition

v0.25.0:
  - util: Removed authkem from HPKE implementation as it is going to be removed from the RFC9180bis spec and is unused in GNUnet anyway.
  - core: New AKE implementation.
  - pils: New service.
  - gns: Various improvements to performance and DNS migration tooling.
  - build: Retired autotools.

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