First draft of logging functionality.

[Michal Sojka]

On Mon, 11 Oct 2010, david at tethera.net wrote:
> The patches following this message are my first attempt at
> implementing atomic logging for notmuch.  The idea is that such logs
> could be useful in synchronizing notmuch instances.
> 
> Feedback of any kind is welcome. I'm particularly interested in
> comments about the log format and performance.

Hi David,

I'm not sure whether implementing logging facility outside of notmuch
library is a good thing. If somebody will use a third-party tool (such
as python bindings) to manipulate his tags, they won't appear in the
log.

-Michal