[RFA-Darwin]: Add an info key in darwin executable

[Joel Brobecker]

> 2009-10-05  Tristan Gingold  <gingold@adacore.com>
>
> 	* darwin-nat.c: Add __TEXT __info_plist content.
> 	(darwin_attach_pid): Update error message.

This looks fine to me. It looks safe for the 7.0 branch as well.
What do you think?

-- 
Joel