Performance test improvements, v2

[Austin Clements]

This series LGTM except the few nits I pointed out.

On Wed, 05 Dec 2012, david at tethera.net wrote:
> This obsoletes the several tests and loose patches posted in thread
>
>      id:1354583824-10520-1-git-send-email-david at tethera.net
>
> The main changes introduced here are caching, and some non-trivial
> tags are used in the dump restore tests.
>
> Caching now makes it sane to split the tests into several files, and
> the output is tidied up a bit for the multi-file case.
>
>
> _______________________________________________
> notmuch mailing list
> notmuch at notmuchmail.org
> http://notmuchmail.org/mailman/listinfo/notmuch