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_buffered_read/psgi.pl

@@ -0,0 +1,17 @@
+use FileHandle;
+
+my $app = sub {
+    my ($environ) = @_;
+
+    $environ->{'psgi.input'}->read(my $body, 1024);
+
+    open my $io, "<", \$body;
+
+    # This makes $io work as FileHandle under 5.8, .10 and .11.
+    bless $io, 'FileHandle';
+
+    $environ->{'psgix.input.buffered'} = 1;
+    $environ->{'psgi.input'} = $io;
+
+    return ['200', ['Content-Length' => length $body], [$body]];
+};