Tests: skip tests with unix domain sockets on win32.

The unix domain sockets are not supported on this platform.
diff --git a/lib/Test/Nginx.pm b/lib/Test/Nginx.pm
index 485c192..d17dbd5 100644
--- a/lib/Test/Nginx.pm
+++ b/lib/Test/Nginx.pm
@@ -176,6 +176,10 @@
 		return $^O ne 'MSWin32' || $self->has_version('1.9.0');
 	}
 
+	if ($feature eq 'unix') {
+		return $^O ne 'MSWin32';
+	}
+
 	return 0;
 }
 
diff --git a/proxy_unix.t b/proxy_unix.t
index 6f63735..e3dd10b 100644
--- a/proxy_unix.t
+++ b/proxy_unix.t
@@ -26,7 +26,7 @@
 eval { require IO::Socket::UNIX; };
 plan(skip_all => 'IO::Socket::UNIX not installed') if $@;
 
-my $t = Test::Nginx->new()->has(qw/http proxy/)->plan(4);
+my $t = Test::Nginx->new()->has(qw/http proxy unix/)->plan(4);
 
 $t->write_file_expand('nginx.conf', <<'EOF');