Merge #1055 -- Prevent opening and parsing files which haven't been modified since the last time that the render was done.

overviewer_core/tileset.py

@@ -24,6 +24,7 @@ import functools
 import time
 import errno
 import stat
+import platform
 from collections import namedtuple
 from itertools import product, izip, chain
 
@@ -760,8 +761,8 @@ class TileSet(object):
         #       Compare the last modified time of the chunk and tile. If the
         #       tile is older, mark it in a RendertileSet object as dirty.
 
-        for chunkx, chunkz, chunkmtime in self.regionset.iterate_chunks():
 
+        for chunkx, chunkz, chunkmtime in self.regionset.iterate_chunks() if (markall or platform.system() == 'Windows') else self.regionset.iterate_newer_chunks(last_rendertime): 
             chunkcount += 1
 
             if chunkmtime > max_chunk_mtime: