Memory usage didn't include path (adp->path), neighbor cache
(adp->neighbor_coords, adp->neighbor_nodes), and the hash table
(adp->hashtab).
While there, print path length.
To get A* statistics on stderr, compile with AS_STATS defined.
other. Ensure headers in include/ can be included in any order
(except for econfig-spec.h, which is special). New header types.h to
help avoid inclusion cycles. Sort include directives. Remove some
superflous includes.
