Apply the second version of SF patch http://www.python.org/sf/536241

Add a method zfill to str, unicode and UserString and change
Lib/string.py accordingly.

This activates the zfill version in unicodeobject.c that was
commented out and implements the same in stringobject.c. It also
adds the test for unicode support in Lib/string.py back in and
uses repr() instead() of str() (as it was before Lib/string.py 1.62)
diff --git a/Misc/NEWS b/Misc/NEWS
index 400b631..a1f5f54 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -6,6 +6,10 @@
 
 Core and builtins
 
+- A method zfill() was added to str and unicode, that fills a numeric
+  string to the left with zeros.  For example,
+  "+123".zfill(6) -> "+00123".
+
 - Complex numbers supported divmod() and the // and % operators, but
   these make no sense.  Since this was documented, they're being
   deprecated now.