Remove MultiLock implementation

Currently the Curses code is broken. Importing offlineimap.ui.Curses
will not succeed due to cyclic imports (threadutils imports ui, but ui
wants threadutils.MultiLock). So Curses cannot be chosen.

Incidentally, the only part in the code that uses "MultiLock" is the
Curses UI, to prevent concurrent access from several threads to the
ui-internal thread list and to IO resources such as the
screen. Fortunately for these purposes we don't need a MultiLock, so we
can do away with that implementation completely. A simple RLock that
allows us to have a thread "own" a lock and makes other threads wanting
access to the resource wait until the owning thread is finished.

The MultiLock implementation looked a bit weird, so simplifying code
here is a good thing, it might well be that we fix some "hangs" that
have been reported (and that would only ever occur with the Curses UI).

Signed-off-by: Sebastian Spaeth <Sebastian@SSpaeth.de>
Signed-off-by: Nicolas Sebrecht <nicolas.s-dev@laposte.net>

offlineimap/ui/Blinkenlights.py

@@ -16,10 +16,9 @@
 #    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 threading import RLock, currentThread
 from offlineimap.ui.UIBase import UIBase
 import thread
-from offlineimap.threadutil import MultiLock
 
 class BlinkenBase:
     """This is a mix-in class that should be mixed in with either UIBase
@@ -85,7 +84,8 @@ class BlinkenBase:
     def init_banner(s):
         s.availablethreadframes = {}
         s.threadframes = {}
-        s.tflock = MultiLock()
+        #tflock protects the s.threadframes manipulation to only happen from 1 thread
+        s.tflock = RLock()
 
     def threadExited(s, thread):
         threadid = thread.threadid