[notmuch] Patches in support of linking from org-mode

[david at tethera.net]

These two patches are pretty much independent. The first is needed by my 
work in progress patch for org-mode to provide links into notmuch 
(http://pivot.cs.unb.ca/git/?p=org-mode.git;a=shortlog;h=refs/heads/notmuch-link).

The second changes the interface of git-show to take the query-string
recently added explicitly as a parameter. This is more an aesthetic
thing, but it means that I don't have to call notmuch-show like
(let notmuch-query-search-string thread-id
     (notmuch-show thread-id))

Hope you like em. I also hope this whole git-send-email thing works out.

David