DES's keyschedules.

I know these two should be separate, and I'll back out the DES changes if they
are deemed to be an error.

Note that there is a memory leak lurking in SSL somewhere in this version.

des_encrypt() and des_encrypt() defined on some systems (Solaris and
Unixware and maybe others), we rename des_encrypt() to des_encrypt1().
This should have very little impact on external software unless
someone has written a mode of DES, since that's all des_encrypt() is
meant for.

(meaning pointer to char) to des_cblock * (meaning pointer to
array with 8 char elements), which allows the compiler to
do more typechecking.  (The changed argument types were of type
des_cblock * back in SSLeay, and a lot of ugly casts were
used then to turn them into pointers to elements; but it can be
done without those casts.)

Introduce new type const_des_cblock -- before, the pointers rather
than the elements pointed to were declared const, and for
some reason gcc did not complain about this (but some other
compilers did).