New Python/Guile Unwinder API wiki page

Hi folks,

I've created a new wiki page to collect information on the
Python/Guile Unwinder APIs:

 https://sourceware.org/gdb/wiki/UnwinderAPI

The intention is to collect information that isn't gdb manual
material, but that would help anyone making use of the API.
Things like links to current users of the APIs, past discussions that
might help one avoid potential pitfalls, suggestions, etc.

The page is pretty empty right now, with just a few links to Andy
Wingo's v8/guile scripts, and Tom Tromey's spidermonkey/python scripts.

Everyone, please do feel free to edit the page at will.  E.g., more
and/or better urls would be greatly appreciated.

I'm pretty clueless on the APIs myself, though I've been getting
questions about it, and my hope is that a centralized hub
will help.  :-)

Thanks,
Pedro Alves