[RFC - doc] Add note about the possibility of symbols getting moved across blocks

[Siva Chandra]

On Sat, Apr 28, 2012 at 12:21 PM, Eli Zaretskii <eliz@gnu.org> wrote:

> Thanks.  If everyone is happy, then so am I.

I think Doug has also OK-ed it.  If I do not see any objections, I
will commit it in couple of days.

Thanks,
Siva Chandra