r2641: talloc_p() now produces a named talloc pointer, with the name

r2641: talloc_p() now produces a named talloc pointer, with the name
auto-derived from the type you are allocating. This is done with
basically zero overhead by relying on the stringify operator in cpp
producing string constants.

the result is that --leak-check nicely names all pointers that come
from talloc_p()