perlPackages.{CryptCurve25519,MathGMP}: fixed build failures

ZHF: #80379
https://hydra.nixos.org/build/112817446
https://hydra.nixos.org/build/112813918
https://hydra.nixos.org/build/112814931
https://hydra.nixos.org/build/112833536
https://hydra.nixos.org/build/112804942
https://hydra.nixos.org/build/112809869

perlPackages.CryptCurve25519: apply patch from gentoo to fix fmul conflicting
types build breakage.
https://gitweb.gentoo.org/repo/gentoo.git/commit/dev-perl/Crypt-Curve25519?id=e07299f804a8376bb5bf85d28916e0a360199f3e

perlPackages.MathGMP: 2.19 -> 2.20
Updated to latest upstream, which passes tests. This is a dependency of
perlPackages.NetSSH