Modify splituser() method to allow an @ in the userinfo field.

Jeremy reported that this is not allowed by RFC 2396; however,
other tools support unescaped @'s so we should also.

Apply SF patch 596581 closing bug 581529.

Lib/urllib.py

@@ -968,7 +968,7 @@ def splituser(host):
     global _userprog
     if _userprog is None:
         import re
-        _userprog = re.compile('^([^@]*)@(.*)$')
+        _userprog = re.compile('^(.*)@(.*)$')
 
     match = _userprog.match(host)
     if match: return map(unquote, match.group(1, 2))