* Add allocation-free C++ AEAD codecs
src/crypto/aead.hpp implements the SIP004/SIP007 AEAD ciphers as value
types: AeadEngine holds the libsodium or Mbed TLS GCM state by value,
AeadTcpEncryptor/AeadTcpDecryptor frame the chunk stream with a fixed
reassembly buffer, and aead_udp_seal/open handle packets. HKDF-SHA1 runs
on stack SHA-1 state instead of Mbed TLS's allocating HMAC API.
The bundled Mbed TLS config now enables MBEDTLS_BLOCK_CIPHER_C, which
keeps the AES context inside mbedtls_gcm_context, so GCM key setup no
longer allocates. That alone saves the C programs two allocations per
connection.
test_crypto_aead_cpp checks HKDF against RFC 5869 and crypto_hkdf, runs
TCP streams and UDP packets between the C and C++ implementations in
both directions for all five AEAD methods, and covers tampering,
framing and salt replay. alloc_steady_crypto_aead runs it under the
malloc counter and requires zero allocations across 600 new
connections and 600 packets (tests/alloc_audit/check_steady.py).
ss_strict_warnings() now applies -Wextra per source file so targets
mixing new C++ with converted C modules keep the latter at -Wall, and
Result gains move assignment.
* Include <algorithm> for std::min in test_crypto_aead_cpp.cpp
* Build the C++ AEAD codecs against Mbed TLS 2.x
Mbed TLS 2 returns void from mbedtls_sha1_starts/update/finish (the int
versions are the _ret variants), which the system-library build on
Ubuntu (2.28) rejects. crypto/mbedtls_compat.hpp gives one int-returning
spelling for both.
* Include C++ headers before crypto.h in test_crypto_aead_cpp.cpp
crypto.h defines min/max macros for the C sources; libstdc++ headers
included after it fail to parse.
* Disable the zero-allocation checks with a system Mbed TLS
They hold for the bundled Mbed TLS (MBEDTLS_BLOCK_CIPHER_C); a system
one may allocate in GCM key setup, as the Debian package build shows.
