digest          defined ENABLE_DIGEST
https           defined HAVE_SSL
ipv6            defined ENABLE_IPV6
iri             defined ENABLE_IRI
large-file      SIZEOF_OFF_T >= 8 || defined WINDOWS

nls             defined ENABLE_NLS
ntlm            defined ENABLE_NTLM
opie            defined ENABLE_OPIE
psl             defined HAVE_LIBPSL

metalink        defined HAVE_METALINK
gpgme           defined HAVE_GPGME

ssl choice:
    openssl     defined HAVE_LIBSSL || defined HAVE_LIBSSL32
    gnutls      defined HAVE_LIBGNUTLS