Don't pick up docblocks from Name nodes

We pick up docblocks from non-documentable elements and assign them to hooks when we think that they belong to one. This PR makes it so that we don't do this for `Name` nodes, because even though they aren't documentable, they still carry the docblock from their corresponding class/constant/function/etc. that they are the name of. If we don't ignore them, we'll end up picking up docblocks that are already associated with a named element, and so aren't really from a non-documentable element after all.

The practical result of this is that a hook which isn't documented (or whose docs we don't pick up, see #128) would no longer be assigned the docs from the last documented element.