crypto: delete dead helpers (ccm, fortuna, aes_pure, gen_tables)
Warnings 32 (unused value), 34 (unused type):
- lib/ccm: [crypto_core] was the non-_into variant, superseded by
[crypto_core_into]. The latter is used by every caller; the wrapper
was never exercised.
- rng/fortuna: [Sha_d256.t] and [Sha_d256.digest] — the module is
used but only through [ctx], [empty], [get], [digesti], [feedi]. The
other two were left over from an earlier shape.
- lib/ocaml/aes_pure: [interleave_in] — the comment just below it
explicitly calls it superseded ("The above is a compact version that
handles one half-block; for the full pipeline we use a different
layout").
- ec/gen_tables: delete unused [div_round_up]; change [let go = ...]
script body to the idiomatic [let () = ...].