* enc-proto.h, enc_des.c, encrypt.c: Unsigned/signed cleanups

   * enc-proto.h, enc_des.c, encrypt.c: Unsigned/signed cleanups

        * forward.c: Include unistd.h if present on machine.

        * misc-proto.h misc.c (auth_encrypt_user): Declare argument as
        const.

        * auth.c: Cast argument auth_encrypt_user. auth_gen_printsub() and
        auth_printsub() take unsigned int as buffer length.

        * auth.h, auth-proto.h, kerberos.c, kerberos5.c, spx.c:
        auth_gen_printsub(), auth_printsub(), kerberos4_printsub(),
        kerberos5_printsub(), spx_printsub() take unsigned int as length
        argument.

        * configure.in: Check for unistd.h

git-svn-id: svn://anonsvn.mit.edu/krb5/trunk@15010 dc483132-0cff-0310-8789-dd5450dbe970