Add missing "void" to prototypes.

Commit 5910d6c7 got this wrong.

Report and patch by Andrew Gierth.

Discussion: http://postgr.es/m/8736diaj98.fsf@news-spur.riddles.org.uk

src/backend/postmaster/autovacuum.c

@@ -311,7 +311,7 @@ NON_EXEC_STATIC void AutoVacLauncherMain(int argc, char *argv[]) pg_attribute_no
 
 static Oid	do_start_worker(void);
 static void HandleAutoVacLauncherInterrupts(void);
-static void AutoVacLauncherShutdown() pg_attribute_noreturn();
+static void AutoVacLauncherShutdown(void) pg_attribute_noreturn();
 static void launcher_determine_sleep(bool canlaunch, bool recursing,
 									 struct timeval *nap);
 static void launch_worker(TimestampTz now);

src/backend/postmaster/checkpointer.c

@@ -161,7 +161,7 @@ static pg_time_t last_xlog_switch_time;
 
 /* Prototypes for private functions */
 
-static void HandleCheckpointerInterrupts();
+static void HandleCheckpointerInterrupts(void);
 static void CheckArchiveTimeout(void);
 static bool IsCheckpointOnSchedule(double progress);
 static bool ImmediateCheckpointRequested(void);