This enables the automatic docstring generation for the Python API.
It's unfortunately only very basic: Just the method signatures without even the argument names. I was hoping it would at least also take the argument names of the signature into account, but it doesn't. :-( The only way towards better docstrings, apart from this, seems to be to hand-craft docstrings in the sip files.
But I think this is better than nothing? I don't see any reason not to enable it.