feat(xan): Generate random villages

This algorithm is a little rough around the edges right now, but
generally the idea is we find a relatively closed-off region of the map,
and place rooms randomly on it, expanding them until they run into each
other, then we put doors in the walls of the rooms and a single door
opening into the region. Later on, we'll generate friendly (or
unfriendly!) NPCs to put in those rooms.

Change-Id: Ic989b9905f55ad92a01fdf6db11aa57afb4ce383
Reviewed-on: https://cl.tvl.fyi/c/depot/+/726
Reviewed-by: glittershark <grfn@gws.fyi>

users/glittershark/xanthous/src/Xanthous/Util/Graphics.hs

@@ -128,6 +128,8 @@ line pa@(xa, ya) pb@(xb, yb)
         (newY, newError) = if (2 * tempError) >= δx
                            then (yTemp + ystep, tempError - δx)
                            else (yTemp, tempError)
+{-# SPECIALIZE line :: (Int, Int) -> (Int, Int) -> [(Int, Int)] #-}
+{-# SPECIALIZE line :: (Word, Word) -> (Word, Word) -> [(Word, Word)] #-}
 
 straightLine :: (Num i, Ord i) => (i, i) -> (i, i) -> [(i, i)]
 straightLine pa@(xa, _) pb@(_, yb) = line pa midpoint ++ line midpoint pb