complete s3fs_readdir() refactor
- multi interface now batches HTTP requests
- proper HTTP KeepAlive sessions are back! (CURLOPT_FORBID_REUSE is no longer required)
- use xpath to quickly grab xml nodes
- lots of cleanup
- fixes some strange stat cache behavior
- huge readdir performance benefits (8-14x in my case) on large directories
git-svn-id: http://s3fs.googlecode.com/svn/trunk@348 df820570-a93a-0410-bd06-b72b767a4274