shsUpdate should take an unsigned int for length

shsUpdate should take an unsigned int for length

Update shsUpdate to take an unsigned int length instead of signed.
The code already assumes that it is an integer >= 0. This change
cleans up a number of signed/unsigned warnings.

sha1/shs.h, shs.c, t_shs.c: change ints to unsigned int
dk/dk_encrypt.c: static function trunc_hmac change a signed int to unsigned
hash_provider/hash_sha1.c: Remove cast in argument to shsUpdate

ticket: new

git-svn-id: svn://anonsvn.mit.edu/krb5/trunk@17945 dc483132-0cff-0310-8789-dd5450dbe970