util: use set instead of dict

util: use set instead of dict

--- a/mercurial/util.py	Tue May 19 11:39:12 2009 +0200
+++ b/mercurial/util.py	Tue May 19 09:57:06 2009 +0200
@@ -266,7 +266,7 @@
             res += re.escape(c)
     return head + res + tail
 
-_globchars = {'[': 1, '{': 1, '*': 1, '?': 1}
+_globchars = set('[{*?')
 
 def pathto(root, n1, n2):
     '''return the relative path from one place to another.