Some lua state allocator fixes

Run GC on the themeroom lua states, as they're not freed
until end of game.

Allocate the exact amount of data we use instead of padding it.

Free our state data after closing the lua state; doing it
the other way is the way to madness, which was kept at bay
by the padded allocation amount.

src/mklev.c

@@ -335,6 +335,7 @@ makerooms(void)
         wallification(1, 0, COLNO - 1, ROWNO - 1);
         free(gc.coder);
         gc.coder = NULL;
+        lua_gc(themes, LUA_GCCOLLECT);
     }
 }