Try to unbreak 021_row_visibility.pl on mingw.

Thanks to Andrew for proposing and testing this fix.

It's possible that we should address this on a more fundamental basis,
e.g. by configuring PerlIO to to CR/LF conversion for us, but this
approach already exists in other places. And it's nice to unbreak the
BF.
Proposed-By: Andrew Dunstan <andrew.dunstan@2ndquadrant.com>
Discussion: https://postgr.es/m/2355d1f0-0244-da9c-ef0c-7542b944e1ac@2ndQuadrant.com

src/test/recovery/t/021_row_visibility.pl

@@ -6,6 +6,7 @@ use warnings;
 use PostgresNode;
 use TestLib;
 use Test::More tests => 10;
+use Config;
 
 # Initialize primary node
 my $node_primary = get_new_node('primary');
@@ -167,6 +168,9 @@ sub send_query_and_wait
 	$$psql{run}->pump_nb();
 	while (1)
 	{
+		# See PostgresNode.pm's psql()
+		$$psql{stdout} =~ s/\r\n/\n/g if $Config{osname} eq 'msys';
+
 		last if $$psql{stdout} =~ /$untl/;
 
 		if ($psql_timeout->is_expired)