Replace thread.get_ident()

Replace low-level thread.get_ident() with threading.currentThread().ident.
This works both in python2.6 and python3. (thread is renamed _thread and its
direct use is not recommended)

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

offlineimap/ui/Curses.py

@@ -16,7 +16,6 @@
 #    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301 USA
 
 from threading import RLock, currentThread, Lock, Event
-from thread import get_ident	# python < 2.6 support
 from collections import deque
 import time
 import sys