Import of hadoop 2.6.0 libhdfs

This version contains major bug fixes and general improvements.
Modified setup to use the new libhdfs.

The idea is to backport the 2.6.0 libhdfs to all 2.x versions of pydoop.
Fixed a missing errno reset bug.

Errno was not reset by hdfsListDirectory and this would break the python
driving code that is expecting to be able to resolve empty directories
from erros by looking at errno.
Minor cleanup in setup.py
Removed duplicated code
Merge pull request #69 from elzaggo/libhdfs_backport

Libhdfs backport