Separate the DES encrypt and decrypt operations into separate functions,

Separate the DES encrypt and decrypt operations into separate functions,
since they have almost no code in common.

* f_cbc.c (krb5int_des_cbc_encrypt, krb5int_des_cbc_decrypt): New functions
broken out from mit_des_cbc_encrypt.
(mit_des_cbc_encrypt): Call them.
* d3_cbc.c (krb5int_des3_cbc_encrypt, krb5int_des3_cbc_decrypt):  New functions
broken out from mit_des3_cbc_encrypt.
(mit_des3_cbc_encrypt): Call them.
* des_int.h (krb5int_des_cbc_encrypt, krb5int_des_cbc_decrypt,
krb5int_des3_cbc_encrypt, krb5int_des3_cbc_decrypt): Declare.
(mit_des_cbc_encrypt, mit_des3_cbc_encrypt): New macros.

git-svn-id: svn://anonsvn.mit.edu/krb5/trunk@15692 dc483132-0cff-0310-8789-dd5450dbe970