Ensure all *.[ch] files include config.h

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.

i3bar/include/child.h

@@ -9,6 +9,8 @@
  */
 #pragma once
 
+#include <config.h>
+
 #include <stdbool.h>
 
 #define STDIN_CHUNK_SIZE 1024

i3bar/include/common.h

@@ -7,6 +7,8 @@
  */
 #pragma once
 
+#include <config.h>
+
 #include <stdbool.h>
 #include <xcb/xcb.h>
 #include <xcb/xproto.h>

i3bar/include/configuration.h

@@ -9,6 +9,8 @@
  */
 #pragma once
 
+#include <config.h>
+
 #include "common.h"
 
 typedef enum {

i3bar/include/ipc.h

@@ -9,6 +9,8 @@
  */
 #pragma once
 
+#include <config.h>
+
 #include <stdint.h>
 
 /*

i3bar/include/mode.h

@@ -9,6 +9,8 @@
  */
 #pragma once
 
+#include <config.h>
+
 #include <xcb/xproto.h>
 
 #include "common.h"

i3bar/include/outputs.h

@@ -9,6 +9,8 @@
  */
 #pragma once
 
+#include <config.h>
+
 #include <xcb/xcb.h>
 #include <cairo/cairo-xcb.h>
 

i3bar/include/parse_json_header.h

@@ -10,6 +10,8 @@
  */
 #pragma once
 
+#include <config.h>
+
 #include <stdint.h>
 
 /**

i3bar/include/util.h

@@ -7,6 +7,8 @@
  */
 #pragma once
 
+#include <config.h>
+
 #include "queue.h"
 
 /* Get the maximum/minimum of x and y */

i3bar/include/workspaces.h

@@ -9,10 +9,10 @@
  */
 #pragma once
 
-#include <xcb/xproto.h>
-
 #include "common.h"
 
+#include <xcb/xproto.h>
+
 typedef struct i3_ws i3_ws;
 
 TAILQ_HEAD(ws_head, i3_ws);

i3bar/include/xcb.h

@@ -9,6 +9,8 @@
  */
 #pragma once
 
+#include <config.h>
+
 #include <stdint.h>
 //#include "outputs.h"