We're not likely to run out of work to do anytime soon...
When a thread has been entirely read, start out by closing all
messages except those that matched the search terms.
+Add support for choosing from one of the user's configured email
+addresses for the From line.
+
+Make 'notmuch-show-pipe-message have a private history.
+
Portability
-----------
Fix configure script to test each compiler warning we want to use.