Bugfix: Saving the NBTTag file format is alot faster, when a BufferedOutputStream is used as another layer, to buffer the input of the GZIPOutputStream. The larger the data, the more of an impact this bug has. This issue has become very noticable with the saving of structure files since 1.6.4, mainly because of the file Mineshaft.dat. But it is not limited to the structures. This code is used in many other places throughout the server code as well, which may benefit from this fix.