Don't declare things in more than one place. Move some declarations

between headers.  Code is now fully prototyped and compiles cleanly
with gcc -Wstrict-prototypes -Wmissing-prototypes -Wnested-externs
-Wredundant-decls.  Closes #723788.

src/server/shutdown.c

@@ -39,6 +39,7 @@
 #include "nat.h"
 #include "file.h"
 #include <time.h>
+#include "server.h"
 #include "prototypes.h"
 
 int shutdown_pending;