Wrote a small shim on top of syslog.

This will allow me to trace issues as I continue refactoring the event
mechanism.
Made SysLog::set_priority return the logger.

This allows SysLog::set_priority to be called inline, instead
of before logging.
typedef'd a bunch of iterators.

There are now five new types:

 - ClientManager::ClientIconIterator
 - ClientManager::WindowIterator
 - ClientContainer::iterator (for iterating over the client state map)
 - LayerManager::iterator (for iterating over the layer map)
 - DesktopManager::iterator (for iterating over the desktop map)
Added the Doxygen /** @file */ header to files that were missing them.