Name clash with standard library's syslog module

Hello

Since the big modules reorg, I've got the following error with the syslog module:

```
2013-07-02 10:18:56,882 [1372753136] Info :    [broker-1] Get a Syslog broker for plugin Syslog
2013-07-02 10:18:56,882 [1372753136] Error :   [broker-1] The module Syslog raised an exception 'module' object has no attribute 'LO
G_USER', I remove it!
2013-07-02 10:18:56,882 [1372753136] Error :   [broker-1] Back trace of this remove: Traceback (most recent call last):
  File "/data/shinken-source/shinken/modulesmanager.py", line 182, in get_instances
    inst = module.get_instance(mod_conf)
  File "/data/shinken-source/modules/syslog/module.py", line 51, in get_instance
    facility = syslog.LOG_USER
AttributeError: 'module' object has no attribute 'LOG_USER'
```

This is due to a name clash between standard library's syslog module and Shinken's syslog module.

Here is commit fixing it by renaming the module's directory.