emacs: Autoload notmuch-jump-search only once

This function is being autoloaded using an autoload cookie, so it
shouldn't additionally be autoloaded using an `autoload' form.

When building libraries we don't actually load the autoloads file and
dropping the `autoload' form results in an error, which reveals a so
far unspecified dependency: `notmuch-tree' needs `notmuch-jump'.

Before this commit compiling (or even just loading) `notmuch-tree'
resulted in `notmuch-jump' being loaded because the former requires
`notmuch-lib', which autoloaded `notmuch-jump-search'.

The bug was that this dependency was not explicitly specified, which
we fix by adding the respective `require' form.

emacs/notmuch-lib.el

@@ -35,9 +35,6 @@
   (defconst notmuch-emacs-version "unknown"
     "Placeholder variable when notmuch-version.el[c] is not available."))
 
-(autoload 'notmuch-jump-search "notmuch-jump"
-  "Jump to a saved search by shortcut key." t)
-
 (defgroup notmuch nil
   "Notmuch mail reader for Emacs."
   :group 'mail)

emacs/notmuch-tree.el

@@ -33,6 +33,7 @@
 (require 'notmuch-show)
 (require 'notmuch-tag)
 (require 'notmuch-parser)
+(require 'notmuch-jump)
 
 (declare-function notmuch-search "notmuch"
 		  (&optional query oldest-first target-thread target-line))