This patch removes includes that are not used. The removals were found with
include-what-you-use which checks if any of the symbols from a header is
in use.
If we test the policy against multiple destination names, we really should
not print warnings if one of the names results in DENY. Instead, pass the
whole array of names to the policy and let it deal with it.
This implements a shared policy cache with read-write locks. We no longer
parse the XML policy in each thread.
This will allow us to easily implement ReloadConfig().
The 'at_console' policy-category allows to apply policy-items to clients
depending on whether they're run from within a valid user-session or not.
We use sd_uid_get_seats() to check whether a user has a valid seat (which
excludes remote-sessions like ssh).