aga_dijkstra_all_paths() runs Dijkstra's algorithm to completion (as
opposed to aga_dijkstra_path(), which operates lazily).  In effect this
computes the shortest path to all (reachable) nodes from the start node.

So, in this context the name makes sense.  But for an analogous function
for future algorithms (e.g. Bellman-Ford), the name doesn't make sense.

So, in the interests of consistency with those future extensions, change
the name of this to aga_dijkstra_complete().
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>