gpg: Add algo constants for PQC.
* common/openpgpdefs.h (PUBKEY_ALGO_KY768_25519): New. (PUBKEY_ALGO_KY1024_448): New. (PUBKEY_ALGO_DIL3_25519): New. (PUBKEY_ALGO_DIL5_448): New. (PUBKEY_ALGO_SPHINX_SHA2): New. * g10/keygen.c (parse_key_parameter_part): Force v5 keys for these algos. * g10/keyid.c (pubkey_string): Add mapping. * g10/misc.c (openpgp_pk_algo_usage): Add standard key usage.
See draft-wussler-openpgp-pqc-01.txt for the code points. To limit
the number of algorithms, only MUST and SHOULD algorithms are
considered.