updated dependencies
increase/decrease the connections counter only when a new context is created/destroyed
allow to drop the specific resource

instead of blindly evict whatever is now in the cache for a specific key

and also use ht_delete_if_equals() now provided by libhl
as optimization and extra safety (so we don't end up removing
something which is not what was supposed to be removed)
use arc_drop_resources() where it makes sense to