While enums are presented much more clearly in the docs and the values didn't
change this apparently caused some issues so we're going back to using #defines.
Also update the docs changing the \var tags to \def tag and putting the description
in a \brief tag.
* Add a note to stop_watching() about the asynchronous nature of node
monitoring and its consequences.
* Also update the breif description and parameters of stop_watching().
* Detail the return values of stop_watching() a bit better.
* Add a note (an \attention actually) to B_STOP_WATCHING flag.
* Fix a spelling mistake and other minor fixes.
