i3bar: Make header declarations extern

See #3914

i3bar/src/config.c

@@ -19,6 +19,7 @@
 
 #include <X11/Xlib.h>
 
+config_t config;
 static char *cur_key;
 static bool parsing_bindings;
 static bool parsing_tray_outputs;

i3bar/src/main.c

@@ -17,6 +17,8 @@
 #include <getopt.h>
 #include <glob.h>
 
+struct ev_loop *main_loop;
+
 /*
  * Having verboselog(), errorlog() and debuglog() is necessary when using libi3.
  *

i3bar/src/outputs.c

@@ -252,6 +252,7 @@ static yajl_callbacks outputs_callbacks = {
     .yajl_end_map = outputs_end_map_cb,
 };
 
+struct outputs_head *outputs;
 /*
  * Initiate the outputs list
  *

i3bar/src/xcb.c

@@ -140,6 +140,9 @@ static const int tray_loff_px = 2;
 /* Vertical offset between the bar and a separator */
 static const int sep_voff_px = 4;
 
+/* Cached width of the custom separator if one was set */
+int separator_symbol_width;
+
 int _xcb_request_failed(xcb_void_cookie_t cookie, char *err_msg, int line) {
     xcb_generic_error_t *err;
     if ((err = xcb_request_check(xcb_connection, cookie)) != NULL) {