docs: the --with-darwinssl option is available on Apple OSes

dnl

dnl initialize all the info variables

    curl_ssl_msg="no      (--with-{ssl,gnutls,nss,polarssl,cyassl,axtls,winssl} )"

    curl_ssl_msg="no      (--with-{ssl,gnutls,nss,polarssl,cyassl,axtls,winssl,darwinssl} )"

    curl_ssh_msg="no      (--with-libssh2)"

   curl_zlib_msg="no      (--with-zlib)"

   curl_krb4_msg="no      (--with-krb4*)"

   dynamic import symbols.

Apple iOS and Mac OS X

======================

   On recent Apple operating systems, curl can be built to use Apple's

   SSL/TLS implementation, Secure Transport, instead of OpenSSL. To build with

   Secure Transport for SSL/TLS, use the configure option --with-darwinssl. (It

   is not necessary to use the option --without-ssl.) This feature requires iOS

   5.0 or later, or OS X 10.5 ("Leopard") or later.

   When Secure Transport is in use, the curl options --cacert and --capath and

   their libcurl equivalents, will be ignored, because Secure Transport uses

   the certificates stored in the Keychain to evaluate whether or not to trust

   the server. This, of course, includes the root certificates that ship with

   the OS. The --cert and --engine options, and their libcurl equivalents, are

   currently unimplemented in curl with Secure Transport.

   For OS X users: In OS X 10.8 ("Mountain Lion"), Apple made a major

   overhaul to the Secure Transport API that, among other things, added

   support for the newer TLS 1.1 and 1.2 protocols. To get curl to support

   TLS 1.1 and 1.2, you must build curl on Mountain Lion or later, or by

   using the equivalent SDK. If you set the MACOSX_DEPLOYMENT_TARGET

   environmental variable to an earlier version of OS X prior to building curl,

   then curl will use the new Secure Transport API on Mountain Lion and later,

   and fall back on the older API when the same curl binary is executed on

   older cats. For example, running these commands in curl's directory in the

   shell will build the code such that it will run on cats as old as OS X 10.6

   ("Snow Leopard") (using bash):

      export MACOSX_DEPLOYMENT_TARGET="10.6"

      ./configure --with-darwinssl

      make

IBM OS/2

========

   Building under OS/2 is not much different from building under unix.

        - AVR32 Linux

        - ARM Android 1.5, 2.1

        - ARM INTEGRITY

        - ARM iPhone OS

        - ARM iOS

        - Cell Linux

        - Cell Cell OS

        - HP-PA HP-UX 9.X 10.X 11.X

        - i386 HURD

        - i386 Haiku OS

        - i386 Linux 1.3, 2.0, 2.2, 2.3, 2.4, 2.6

        - i386 Mac OS X

        - i386 MINIX 3.1

        - i386 NetBSD

        - i386 Novell NetWare