title: vim not drawn correctly in tmux
body: <p>I've got some issues with vim in tmux. It is not drawn correctly. I think that the statusbar introduced by tmux messes with the way vim draws its layout.
  When I create two windows, open vim in one of them and switch to the other one and then back to vim, I see this:</p>
  
  <p><img src="https://i.stack.imgur.com/Rb2Nb.jpg" alt="Image of double tmux statusbar"></p>
  
  <p>Also, CtrlP behaves weird. It looks like this when I fire it up:</p>
  
  <p><img src="https://i.stack.imgur.com/34cIC.jpg" alt="CtrlP drawn wrong"></p>
  
  <p>The VIM statusbar is obviously not drawn in this picture. It should be above the CtrlP menu.</p>
  
  <p>The system with this bad behaviour is a debian installation (actually in a chroot inside archlinux). Here is a bit of info about the system and the vim and tmux versions.</p>
  
  <pre><code>(precise32)root@excalibur:llvm-apps# uname -a[5/5]
  Linux excalibur 3.12.5-1-ARCH #1 SMP PREEMPT Thu Dec 12 12:57:31 CET 2013 i686 athlon i386 GNU/Linux
  (precise32)root@excalibur:llvm-apps# tmux -V
  tmux 1.8
  (precise32)root@excalibur:src# vim --version
  VIM - Vi IMproved 7.4 (2013 Aug 10, compiled Jan  9 2014 23:30:55)
  Included patches: 1-135
  Compiled by nathan@excalibur
  Huge version with X11-Athena GUI.  Features included (+) or not (-):
  </code></pre>
  
  <p>Can somebody point me in the right direction?                                                 </p>