Perl: creating input and error streams if closed.

Application handler can do anything with a stream object (including close it).
Once the stream is closed, Unit creates a new stream.

This closes #616 issue on GitHub.

test/perl/input_close/psgi.pl

@@ -0,0 +1,8 @@
+my $app = sub {
+    my ($environ) = @_;
+
+    $environ->{'psgi.input'}->read(my $body, 1024);
+    $environ->{'psgi.input'}->close();
+
+    return ['200', ['Content-Length' => length $body], [$body]];
+};