XI2 has been merged

[Peter Hutterer]

As planned, XI2 has been merged into master today.

You must recompile your input drivers after rebasing master, the ABI has
changed.

Major changes:
- XIAnyModifier works now as a grab modifier
- XIAllDevices and XIAllMasterDevices work are allowed for passive grabs.
- passive grabs on slave devices detach the device until ungrabbed.

And a number of bugs fixed. Many thanks at this point to Thomas Jaeger who
pointed out a number of these.

Lets get this thing ready to ship!

Cheers,
  Peter