Fix -e option in contrib/intarray/bench/bench.pl.

As implemented, -e ran an EXPLAIN but then discarded the output, which
certainly seems pointless.  Make it print to stdout instead.  It's been
like that forever, so back-patch to all supported branches.

Daniel Gustafsson, reviewed by Andreas Scherbaum

Patch: <B97BDCB7-A3B3-4734-90B5-EDD586941629@yesql.se>

contrib/intarray/bench/bench.pl

@@ -92,7 +92,8 @@ if ($opt{v})
 
 if ($opt{e})
 {
-	$dbi->do("explain $sql");
+	my @plan = map { "$_->[0]\n" } @{$dbi->selectall_arrayref("explain $sql")};
+	print @plan;
 }
 
 my $t0    = [gettimeofday];