[RFA/doco] Document that the GNAT runtime should not be stripped

[Joel Brobecker]

> > Okay.  If you want to apply this to active release branches, that's
> > fine as well.
> 
> Thank you! It's a good idea to apply this to the release branch too,
> so I'm checking it out. I will commit there as soon as the checkout
> is complete.

Actually, the commit attempt failed. Maybe I used the wrong branch?
svn://gcc.gnu.org/svn/gcc/branches/gcc-4_1-branch/gcc

It's not terribly important that this patch makes it to the release
branch, however.

-- 
Joel