I called it a bugfix on 0.2.0.10-alpha, since git commit e5885deab is
where we introduced anonymized begin_dir connections.

This solves bug 5283, where client traffic could get sent over the
same circuit as an anonymized connection to a directory, even if
that circuit used an exit node unsuitable for clients.  By marking
the directory connection as needs_internal, we ensure that the
(non-internal!) client-traffic connection won't be sent over the
same circuit.

It turns out that if you set the third argument of
__attribute__(format) to 0, GCC and Clang will check the format
argument without expecting to find variadic arguments.  This is the
correct behavior for vsnprintf, vasprintf, and vscanf.

I'm hoping this will fix bug 5969 (a clang warning) by telling clang that
the format argument to tor_vasprintf is indeed a format string.

(When the correct answer is given in terms of seconds since the
epoch, it's hard to be sure that it really is the right answer
just by reading the code.)