lots of misc cleanups for compiler warnings

ratbox_lib.c:159:1: warning: function 'rb_lib_restart' could be declared
                    with attribute 'noreturn' [-Wmissing-noreturn]

ratbox_lib.c:220:1: warning: function 'rb_lib_loop' could be declared
                    with attribute 'noreturn' [-Wmissing-noreturn]

restart.c:55:1: warning: function 'server_reboot' could be declared with
                attribute 'noreturn' [-Wmissing-noreturn]

include/restart.h

@@ -27,7 +27,7 @@
 #ifndef INCLUDED_restart_h
 #define INCLUDED_restart_h
 
-void restart(const char *);
-void server_reboot(void);
+void restart(const char *) __attribute__((noreturn));
+void server_reboot(void) __attribute__((noreturn));
 
 #endif

libratbox/include/ratbox_lib.h

@@ -179,14 +179,14 @@ typedef void die_cb(const char *buffer);
 char *rb_ctime(const time_t, char *, size_t);
 char *rb_date(const time_t, char *, size_t);
 void rb_lib_log(const char *, ...);
-void rb_lib_restart(const char *, ...);
+void rb_lib_restart(const char *, ...) __attribute__((noreturn));
 void rb_lib_die(const char *, ...);
 void rb_set_time(void);
 const char *rb_lib_version(void);
 
 void rb_lib_init(log_cb * xilog, restart_cb * irestart, die_cb * idie, int closeall, int maxfds,
 		 size_t dh_size, size_t fd_heap_size);
-void rb_lib_loop(long delay);
+void rb_lib_loop(long delay) __attribute__((noreturn));
 
 time_t rb_current_time(void);
 const struct timeval *rb_current_time_tv(void);

libratbox/include/rb_memory.h

@@ -34,7 +34,7 @@
 #include <stdlib.h>
 
 
-void rb_outofmemory(void);
+void rb_outofmemory(void) __attribute__((noreturn));
 
 static inline void *
 rb_malloc(size_t size)

modules/m_restart.c

@@ -95,6 +95,5 @@ mo_restart(struct Client *client_p, struct Client *source_p, int parc, const cha
 
 	rb_sprintf(buf, "Server RESTART by %s", get_client_name(source_p, HIDE_IP));
 	restart(buf);
-
-	return 0;
+	/* UNREACHABLE */
 }

src/ircd.c

@@ -418,7 +418,7 @@ ircd_log_cb(const char *str)
 	ilog(L_MAIN, "libratbox reports: %s", str);
 }
 
-static void
+static void __attribute__((noreturn))
 ircd_restart_cb(const char *str)
 {
 	inotice("libratbox has called the restart callback: %s", str);
@@ -730,6 +730,5 @@ main(int argc, char *argv[])
 		        ConfigFileEntry.dpath, getpid());
 
 	rb_lib_loop(0);
-
-	return 0;
+	/* UNREACHABLE */
 }

ssld/ssld.c

@@ -1257,7 +1257,7 @@ main(int argc, char **argv)
 	if(!ssld_ssl_ok)
 		send_nossl_support(mod_ctl, NULL);
 	rb_lib_loop(0);
-	return 0;
+	/* UNREACHABLE */
 }