use #pragma once instead of foo*foo define guards

src/core/killall.h

@@ -1,7 +1,6 @@
 /*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
 
-#ifndef fookillallhfoo
-#define fookillallhfoo
+#pragma once
 
 /***
   This file is part of systemd.
@@ -23,5 +22,3 @@
 ***/
 
 void broadcast_signal(int sig, bool wait);
-
-#endif

src/core/switch-root.h

@@ -1,7 +1,6 @@
 /*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
 
-#ifndef fooswitchroothfoo
-#define fooswitchroothfoo
+#pragma once
 
 /***
   This file is part of systemd.
@@ -23,5 +22,3 @@
 ***/
 
 int switch_root(const char *switch_root);
-
-#endif

src/core/syscall-list.h

@@ -1,7 +1,6 @@
 /*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
 
-#ifndef foosyscalllisthfoo
-#define foosyscalllisthfoo
+#pragma once
 
 /***
   This file is part of systemd.
@@ -40,5 +39,3 @@ const char *syscall_to_name(int id);
 int syscall_from_name(const char *name);
 
 int syscall_max(void);
-
-#endif

src/core/transaction.h

@@ -1,7 +1,6 @@
 /*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
 
-#ifndef footransactionhfoo
-#define footransactionhfoo
+#pragma once
 
 /***
   This file is part of systemd.
@@ -53,5 +52,3 @@ int transaction_add_job_and_dependencies(
 int transaction_activate(Transaction *tr, Manager *m, JobMode mode, DBusError *e);
 int transaction_add_isolate_jobs(Transaction *tr, Manager *m);
 void transaction_abort(Transaction *tr);
-
-#endif