libxtreemfs-async: TLS interrupt implementation with __thread (fails at...

libxtreemfs-async: TLS interrupt implementation with __thread (fails at runtime for some mysterious dynamic library related reason - committed for documentation, will be replaced soon)

git-svn-id: https://xtreemfs.googlecode.com/svn/branches/mno-async_writes@2996 f8528748-c2c0-11dd-ba5c-d3b7c2b3b534