Use lua for special level files

Game is playable, and should compile on linux and Windows.
Assumes you have a lua 5.3 library available.

Removes level compiler and associated files.
Replaces special level des-files with lua scripts.
Exposes some NetHack internals to lua:
 - des-table with commands to create special levels
 - nh-table with NetHack core commands
 - nhc-table with some constants
 - u-table with some player-specific data (u-struct)
 - selection userdata

Adds some rudimentary tests.

Adds new extended command #wizloadlua to run a specific script,
and #wizloaddes to run a specific level-creation script.

nhlib.lua is loaded for every lua script.

Download and untar lua:
  mkdir lib
  cd lib
  curl -R -O http://www.lua.org/ftp/lua-5.3.5.tar.gz
  tar zxf lua-5.3.5.tar.gz

Then make nethack normally.

src/save.c

@@ -662,10 +662,14 @@ xchar lev;
     saveobjchn(nhfp, g.billobjs);
     if (release_data(nhfp)) {
         int x,y;
-
+        /* TODO: maybe use clear_level_structures() */
         for (y = 0; y < ROWNO; y++)
-            for (x = 0; x < COLNO; x++)
+            for (x = 0; x < COLNO; x++) {
                 g.level.monsters[x][y] = 0;
+                g.level.objects[x][y] = 0;
+                levl[x][y].seenv = 0;
+                levl[x][y].glyph = cmap_to_glyph(S_stone);
+            }
         fmon = 0;
         g.ftrap = 0;
         fobj = 0;