des_quad_cksum() byte order bug fix.

See http://www.pdc.kth.se/kth-krb/

Their solution for CRAY is somewhat awkward.
I'll assume that a "short" is 32 bits on CRAY to avoid the
#ifdef _CRAY
    typedef struct {
        unsigned int a:32;
        unsigned int b:32;
    } XXX;
#else
    typedef DES_LONG XXX;
#endif