Merge branch 'ordered-hashtable'

This changes the hashtable implementation to that it maintains insertion
order.  This is then used in the vici plugin to store connections in a
hash table instead of a linked list, which makes managing them quite a
bit faster if there are lots of connections.

The old implementation is extracted into a new class (hashlist_t), which
optionally supports sorting keys and provides the previous get_match()
function.