Handle the _NET_REQUEST_FRAME_EXTENTS ClientMessage (java compat)

This ClientMessage can be used to estimate how big the window will be
before opening it. Java always sends the ClientMessage and checks the
atom that should be set by the window manager, but it seems that the
fallback code path has a race condition.

Let’s see if the situation gets better with this change. I have been
running this patch for about two weeks and have not seen any issues with
it.

fixes #934
fixes #709
i3bar: draw workspace buttons at x=0 instead of x=1

This makes the workspace buttons align with the window borders, which is
particularly visible with color configurations like the one in this
screenshot: http://i.imgur.com/CH8srF5.png

fixes #687
log.c: use posix_fallocate() instead of ftruncate() (Thanks don)

The effect is that the error handling is much better. posix_fallocate()
will allocate all the requested space, whereas ftruncate() does not.

Before this commit, in case the /dev/shm filesystem is too small to hold
the _contents_ of the log file, i3 will SIGBUS when writing to the shm
logfile. With this commit, it will print an error message on startup,
but continue to run without logging.
add release notes for v4.6
Merge branch 'release-4.6' into next
Merge branch 'next'
update debian/ packaging
Include float.h for DBL_EPSILON

https://bugs.gentoo.org/show_bug.cgi?id=480272

Patch was written by Jeroen Roovers <jer@gentoo.org>
Merge branch 'master' into next
Merge branch 'fix-float-h'
Update documentation paragraph on variables

see http://infra.in.zekjur.net/archives/i3-discuss/2013-August/001377.html
Add missing return after error reporting.
Merge branch 'fix-move-window-center'
Merge branch 'master' into next
Fix userguide formatting (Thanks Slava)
Merge branch 'fix-userguide'
Merge branch 'master' into next