Another round of fixes, including figuring out the memory leak

scripts/ds/deque.lua

@@ -2,7 +2,7 @@
 A double-ended queue based on: https://www.lua.org/pil/11.4.html
 
 That's a long resource.  The idea is much simpler than the chapter: maintain two
-indices for thje bottom and top, then use the fact that Lua allows "moving" the
+indices for the bottom and top, then use the fact that Lua allows "moving" the
 array upward forever at the cost of becoming a hashtable.
 
 This is global-safe.
@@ -61,6 +61,7 @@ function Deque:pop_front()
    local b = self.back
    if b < f then return nil end
    local r = self.items[f]
+   self.items[f] = nil
    self.front = f + 1
    return r
 end
@@ -71,6 +72,7 @@ function Deque:pop_back()
    local b = self.back
    if b < f then return nil end
    local r = self.items[b]
+   self.items[b] = nil
    self.back = b - 1
    return r
 end
@@ -79,6 +81,7 @@ function Deque:clear()
    self.front = 1
    self.back = 0
    self.items = {}
+   self.items = {}
 end
 
 -- Some quick self-tests.

scripts/scanner/backends/trees.lua

@@ -105,6 +105,8 @@ function TreeBackend:dump_entries_to_set(player, set)
       end
    end
 
+   self.point_queue = TH.defaulting_table()
+
    self.clusterer:submit_points(points_flat)
 
    local px, py = player.position.x, player.position.y

scripts/scanner/surface-scanner.lua

@@ -110,7 +110,7 @@ local BACKEND_LUT = {
    ["straight-rail"] = SEB.TrainsSimple,
    ["stream"] = SEB.Other,
    ["tile-ghost"] = SEB.Ghosts,
-   ["train-stop"] = SEB.TrainsNamed,
+   ["train-stop"] = SEB.TrainsSimple,
    ["transport-belt"] = SEB.Logistics,
    ["tree"] = TreeBackend.TreeBackend,
    ["turret"] = SEB.Unit,