[idea] Ease understanding of positional-only and keyword-only makers in function prototyes

Documentation

In https://docs.python.org/dev/library/functions.html I added many / and * markers in function prototypes. There were already a few of them here, and I bet there is some in other places in the doc too.

For newcomers it may look like a typo, and it may be hard for them to discover what it means.

I think it would be nice to tell them what it is, maybe by making all markers a link to the glossary or by displaying a message on mouse hover like « The parameters on the left of a / are positional-only. ».