Add utility function to flatten a node
Add utility function to flatten a node

Sometimes we might want to get only the text structure from a
node (and all its descendents) -- such as in a89467e ("Use
<description> to get return types, not <type>", 2017-03-17). In that
case, we were able to get around it by using an alternate node. Here
we implement the "proper" solution.

angus-g/sphinxcontrib-autodoc_doxygen