* configure.ac: --enable-dtls13 auto-enables --enable-dtls and TLS 1.3,
with a targeted error if either is explicitly --disabled, plus a
post-finalization sanity check that errors out if a later
prerequisite test forces ENABLED_TLS13 back to "no" while
ENABLED_DTLS13 is yes.
* src/internal.c, src/wolfio.c, wolfssl/wolfio.h: new WOLFSSL_DTLS_ONLY
compile-time flag elides the EmbedReceive / EmbedSend default
callbacks. The DTLS_MAJOR runtime check stays in SetSSL_CTX so a
TLS-method ctx in a DTLS-only build doesn't get datagram callbacks
by default, and WriteSEQ keeps its ssl->options.dtls branch. A
#error in settings.h refuses WOLFSSL_DTLS_ONLY without WOLFSSL_DTLS.
* wolfcrypt/src/aes.c: add HAVE_AES_DECRYPT to the inv_col_mul
definition gate to match its only caller; without it the function is
emitted dead under WOLFSSL_AES_DIRECT && NO_AES_DECRYPT and
-Werror=unused-function fails the build.
* .github/workflows/os-check.yml: matrix entry for a minimal DTLS 1.3
client-only build.
Juliusz Sosinowicz
a012a8f3ec