add hash function for ZipInfo objects... This lets us

ensure that two seperate ZipInfo objects that refer to the
same file compare equal..

[git-p4: depot-paths = "//depot/": change = 1573]

ZipStorage.py

@@ -70,12 +70,20 @@ def zipinfocmp(za, zb):
 
 	return 0
 
+def zipinfohash(za):
+	r = 0
+	for i in [ 'filename', 'date_time', 'file_size', 'CRC' ]:
+		r ^= getattr(za, i).__hash__
+
+	return r
+
 class ZIWrap(object):
 	__slots__ = [ '_zi' ]
 
 	def __init__(self, zi):
 		self._zi = zi
 
+	__hash__ = zipinfohash
 	__cmp__ = zipinfocmp
 
 	def __getattr__(self, n):