openpgp: Zero the stack after nettle's ed25519::public_key
libgmp, a dependency of nettle, does not appropriately zero the
input after calling mpn_mul_n
. Because of this, it is possible for
an ed25519 private key to be kept on the stack. This only occurs on
some systems and may depend on the optimization of the compiler
building libgmp.
Fixes: #1080 (closed)