scmutil: add missing import of re stable

scmutil: add missing import of re

see https://bitbucket.org/tortoisehg/thg/issue/929

--- a/mercurial/scmutil.py	Tue Jul 12 12:35:03 2011 -0500
+++ b/mercurial/scmutil.py	Fri Jul 08 20:24:19 2011 -0500
@@ -8,7 +8,7 @@
 from i18n import _
 import util, error, osutil, revset, similar
 import match as matchmod
-import os, errno, stat, sys, glob
+import os, errno, re, stat, sys, glob
 
 def checkfilename(f):
     '''Check that the filename f is an acceptable filename for a tracked file'''