Add the possibility to enable olde des support, not just disable it, for...

  +) Change all functions with names starting with des_ to be starting

     with DES_ instead.  Add wrappers that are compatible with libdes,

     but are named _ossl_old_des_*.  Finally, add macros that map the

     des_* symbols to the corresponding _ossl_old_des_*.

     des_* symbols to the corresponding _ossl_old_des_* if libdes

     compatibility is desired.  If OpenSSL 0.9.6c compatibility is

     desired, the des_* symbols will be mapped to DES_*, with one

     exception.

     All this is done because there are increasing clashes with libdes

     and other DES libraries that are currently used by other projects.

     The old libdes interface (including crypt()) is provided if

     <openssl/des_old.h> is included.  For now, this automatically

     happens in <openssl/des.h> unless OPENSSL_DISABLE_OLD_DES_SUPPORT is

     defined.  Note that crypt() is no longer declared in <openssl/des.h>.

     Since we provide two compatibility mappings, the user needs to

     define the macro OPENSSL_DES_LIBDES_COMPATIBILITY if libdes

     compatibility is desired.  The default (i.e., when that macro

     isn't defined) is OpenSSL 0.9.6c compatibility.

     There are also macros that enable and disable the support of old

     des functions altogether.  Those are OPENSSL_ENABLE_OLD_DES_SUPPORT

     and OPENSSL_DISABLE_OLD_DES_SUPPORT.  If none or both of those

     are defined, the default will apply: to support the old des routines.

     In either case, one must include openssl/des.h to get the correct

     definitions.  Do not try to just include openssl/des_old.h, that

     won't work.

     NOTE: This is a major break of an old API into a new one.  Software

     authors are encouraged to switch to the DES_ style functions.  Some

     time in the future, des_old.h and the libdes compatibility functions

     will be completely removed.

     will be disable (i.e. OPENSSL_DISABLE_OLD_DES_SUPPORT will be the

     default), and then completely removed.

     [Richard Levitte]

  *) Fix SSL handshake functions and SSL_clear() such that SSL_clear()

    } DES_key_schedule;

#ifndef OPENSSL_DISABLE_OLD_DES_SUPPORT

# ifndef OPENSSL_ENABLE_OLD_DES_SUPPORT

#  define OPENSSL_ENABLE_OLD_DES_SUPPORT

# endif

#endif

#ifdef OPENSSL_ENABLE_OLD_DES_SUPPORT

# include <openssl/des_old.h>

#endif