Force output_compression Off for downloads

Looks like a long standing, yet-to-be-fixed PHP bug, where
zlib.output_compression can result in the output buffer not completely being
flushed. This is especially critical for downloads where the tail of the
file might be lost.

https://bugs.php.net/bug.php?id=19436

include/class.file.php

@@ -96,6 +96,7 @@ class AttachmentFile {
     }
 
     function sendData() {
+        @ini_set('zlib.output_compression', 'Off');
         $file = $this->open();
         while ($chunk = $file->read())
             echo $chunk;