[QUICK] talloc bugs

[tridge at samba.org]

Hi Sam,

I should also say that we can still revisit
talloc_reference/talloc_free and look at other models. I think the
commits I just made solve the problem, and they certainly remove the
ambiguity so the main traps with using
talloc_reference/talloc_free/talloc_steal are now gone.

We could consider a more intrusive API change if someone can propose
one that is a significant improvement over the minimal change I just
made.

Cheers, Tridge