tree-wide: Make sure all headers are standalone

Let's make sure all of our headers include everything they require.

src/core/dynamic-user.h

@@ -1,8 +1,8 @@
 /* SPDX-License-Identifier: LGPL-2.1-or-later */
 #pragma once
 
-#include <stdio.h>
 #include <stdbool.h>
+#include <stdio.h>
 #include <sys/types.h>
 
 #include "fdset.h"

src/core/main.h

@@ -3,6 +3,8 @@
 
 #include <stdbool.h>
 
+#include "crash-handler.h"
+
 extern bool arg_dump_core;
 extern int arg_crash_chvt;
 extern bool arg_crash_shell;

src/core/show-status.h

@@ -1,6 +1,7 @@
 /* SPDX-License-Identifier: LGPL-2.1-or-later */
 #pragma once
 
+#include <stdarg.h>
 #include <stdbool.h>
 
 #include "macro.h"

src/core/smack-setup.h

@@ -7,4 +7,6 @@
         Nathaniel Chen <nathaniel.chen@intel.com>
 ***/
 
+#include <stdbool.h>
+
 int mac_smack_setup(bool *loaded_policy);