clang-format: don’t define ForeachMacros

Otherwise clang-formatting **/*.h breaks include/queue.h
clang-format-3.5 **/*.h **/*.c

This should be the last commit that formats a big bunch of files. From
here on, whenever I merge patches, I’ll run clang-format like described
in the title.
Implement EWMH number of desktops property

_NET_NUMBER_OF_DESKTOPS:

> This property SHOULD be set and updated by the Window Manager to
> indicate the number of virtual desktops.

We interpret this property as the number of noninternal workspaces.
bugfix: don't set input focus if not accepted

http://tronche.com/gui/x/icccm/sec-4.html#s-4.1.7

> Clients using the Globally Active model can only use a SetInputFocus request
> to acquire the input focus when they do not already have it on receipt of one
> of the following events:
> * ButtonPress
> * ButtonRelease
> * Passive-grabbed KeyPress
> * Passive-grabbed KeyRelease

Since managing a window happens on a MapNotify (which is absent from this
list), the window cannot accept input focus, so we should not try to focus
the window at all.

Fixes an issue with xfce4-notifyd which (correctly) declines focus when
we send WM_TAKE_FOCUS, which puts i3 in a state where i3 focus and X
focus are different when a notification appears.
tests: explicitly set input hint

Since i3 honors the “Globally Active Input” focus model, we need to
explicitly state that we are not using that in our testcases :).

This requires X11::XCB from git to work (commit
71b25dcaafc509e710b8fd7de20c97ac3549fc39).