libsepol: use constant keys in hashtab functions

Even though "hashtab_key_t" is an alias for "char *", "const
hashtab_key_t" is not an alias for "(const char) *" but means "(char *)
const".

Introduce const_hashtab_key_t to map "(const char) *" and use it in
hashtab_search() and hashtab key comparison functions.

Signed-off-by: Nicolas Iooss <nicolas.iooss@m4x.org>
12 files changed