Trailing underscores in types

Trailing underscores in types in the Parameters and Returns sections have to be escaped in order to not give an Unknown target name warning.

Examples that DON'T work :

def identity(object_):
    """Identity function.

    Parameters
    ----------
    object_ : Any

    Returns
    -------
    object_ : type(object_)
        Just `object_` again.
    """
    return object_

The returns section

Returns
-------
type(object_)
    Just `object_` again.

Without a name doesn't work either. In both cases, I have to write type(object\_).

I don't know if this is fixable like it was for parameter names (#63). I guess types are actually supposed to be links sometimes, in contrast to parameter names? Feel free to close if that is the case and there's just not really a possible fix.

Start by reproducing the Unknown target name warning with the Parameters and Returns examples in the issue. Compare the existing handling described in issue #63 and inspect how numpydoc parses parameter and return types. Done means the shown trailing-underscore forms work without manual escaping while valid type links remain intact.