tree-wide: add several missing includes

- test-reread-partition-table.c: sys/file.h for LOCK_EX
- coredump: unistd.h for STDIN_FILENO

src/coredump/coredump-backtrace.c

@@ -1,5 +1,7 @@
 /* SPDX-License-Identifier: LGPL-2.1-or-later */
 
+#include <unistd.h>
+
 #include "sd-journal.h"
 #include "sd-messages.h"
 

src/coredump/coredump-kernel-helper.c

@@ -1,5 +1,7 @@
 /* SPDX-License-Identifier: LGPL-2.1-or-later */
 
+#include <unistd.h>
+
 #include "coredump-config.h"
 #include "coredump-context.h"
 #include "coredump-kernel-helper.h"

src/test/test-reread-partition-table.c

@@ -1,6 +1,7 @@
 /* SPDX-License-Identifier: LGPL-2.1-or-later */
 
 #include <linux/loop.h>
+#include <sys/file.h>
 
 #include "blockdev-util.h"
 #include "fd-util.h"