Do not import threading.*

Only import the lock, that we actually need. Also import the with statement
for use with python 2.5. We'll need it for sure in this file.

Signed-off-by: Sebastian Spaeth <Sebastian@SSpaeth.de>

offlineimap/folder/UIDMaps.py

@@ -15,8 +15,8 @@
 #    You should have received a copy of the GNU General Public License
 #    along with this program; if not, write to the Free Software
 #    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301 USA
-
-from threading import *
+from __future__ import with_statement # needed for python 2.5
+from threading import Lock
 from IMAP import IMAPFolder
 import os.path