Including config.h is necessary to get e.g. the _GNU_SOURCE define and
any other definitions that autoconf declares. Hence, config.h needs to
be included as the first header in each file.
This is done either via:
1. Including "common.h" (i3bar)
2. Including "libi3.h"
3. Including "all.h" (i3)
4. Including <config.h> directly
Also remove now-unused I3__FILE__, add copyright/license statement
where missing and switch include/all.h to #pragma once.
From the source:
When starting i3 initially (and after each change to the connected
outputs), this function fixes the resolution of the __i3
pseudo-output. When that resolution is not set to a function which
shares a common divisor with every active output’s resolution,
floating point calculation errors will lead to the scratchpad window
moving when shown repeatedly.
fixes#632
Michael Stapelberg