mp_set_memory_functions

gnutls 3.7.5 causes alkimia unit tests to fail (Alkimia is here: https://invent.kde.org/office/alkimia ) because alkimia uses gmp, and gnutls 3.7.5 sets the realloc and free via mp_set_memory_functions, but doesn't set an alloc function.

So __gmp_default_alloc is used for alloc, but gnutls_free_zero is used for free operations.

If what's needed is to have a gnutls_alloc function I can take a stab at adding one tomorrow and will put up an MR after testing, etc.

commit 41c9c845 Author: Tobias Heider tobias.heider@canonical.com Date: Mon Mar 14 16:17:28 2022 +0100

Use custom allocators for GMP to make sure temporary secrets
from cryptographic operations in nettle are deleted safely.

Signed-off-by: Tobias Heider <tobias.heider@canonical.com>

is the commit that breaks things btw.