fix missing includes in gtklaunch

OpenRA.Launcher.Gtk/bridge.c

@@ -8,6 +8,7 @@
 #include <stdlib.h>
 #include <stdio.h>
 #include <string.h>
+#include <unistd.h>
 
 #include <webkit/webkit.h>
 #include <JavaScriptCore/JavaScript.h>

OpenRA.Launcher.Gtk/main.c

@@ -10,6 +10,7 @@
 #include <string.h>
 #include <gtk/gtk.h>
 #include <webkit/webkit.h>
+#include <unistd.h>
 
 #include "main.h"
 #include "server.h"

OpenRA.Launcher.Gtk/server.c

@@ -12,6 +12,7 @@
 #include <stdint.h>
 #include <fcntl.h>
 #include <string.h>
+#include <stdarg.h>
 
 #define MHD_PLATFORM_H
 #include <microhttpd.h>