Clear some style deviations.

src/backend/postmaster/autovacuum.c

@@ -834,7 +834,7 @@ HandleAutoVacLauncherInterrupts(void)
  * Perform a normal exit from the autovac launcher.
  */
 static void
-AutoVacLauncherShutdown()
+AutoVacLauncherShutdown(void)
 {
 	ereport(DEBUG1,
 			(errmsg("autovacuum launcher shutting down")));

src/backend/storage/buffer/freelist.c

@@ -177,7 +177,7 @@ ClockSweepTick(void)
  * should not call this.
  */
 bool
-have_free_buffer()
+have_free_buffer(void)
 {
 	if (StrategyControl->firstFreeBuffer >= 0)
 		return true;

src/backend/storage/smgr/md.c

@@ -1114,7 +1114,7 @@ _mdfd_openseg(SMgrRelation reln, ForkNumber forknum, BlockNumber segno,
 			  int oflags)
 {
 	MdfdVec    *v;
-	int			fd;
+	File		fd;
 	char	   *fullpath;
 
 	fullpath = _mdfd_segpath(reln, forknum, segno);

src/backend/utils/misc/queryenvironment.c

@@ -36,7 +36,7 @@ struct QueryEnvironment
 
 
 QueryEnvironment *
-create_queryEnv()
+create_queryEnv(void)
 {
 	return (QueryEnvironment *) palloc0(sizeof(QueryEnvironment));
 }