Blender Git Loki

Bug fix, after irc report sk1p:

frame-sliding (LMB) in action, nla, sound and ipo window went into very
tight while loop, causing cpu to choke. Added nice idle.

Bug fix, found self while testing:
- relative.blend, editmode
- delete part, exit editmode
- enter editmode, undo twice, exit editmode -> crash

The trick to copy 'old' locations of vertices to keys isnt undo-resistant
yet. This fix at least doesnt crash, but copying doesnt work when undo-ing
back to previous editmode session (indices just differ from current mesh...)