Fix all doxygen "X is not documented" warnings

Quoting arma:

It occurred to me while looking at the doxygen comment for router_is_already_dir_fetching_ds() that if we had something go through and complain about all cases where there's a function argument that is not mentioned by <b>parameter</b> (with the markup) in the doxygen comment... we would end up with a lot of complaints.

We could fix this by placing <b></b> around documented parameters, and by documented undocumented parameters.

There might even be a way to semi-automatically do this using a script, and then clean up any mismatches.