Don't use kill-this-buffer to kill notmuch emacs buffers

kill-this-buffer appears to be a function intended specifically for
use in the menu bar, and causes problem killing notmuch buffers when
multiple frames have been used.  This patch replaces kill-this-buffer
with notmuch-kill-this-buffer, which in turn just simply calls
(kill-buffer (current-buffer)).

emacs/notmuch-hello.el

@@ -294,7 +294,7 @@ should be. Returns a cons cell `(tags-per-line width)'."
     (define-key map "v" '(lambda () "Display the notmuch version" (interactive)
                            (message "notmuch version %s" (notmuch-version))))
     (define-key map "?" 'notmuch-help)
-    (define-key map "q" 'kill-this-buffer)
+    (define-key map "q" 'notmuch-kill-this-buffer)
     (define-key map "=" 'notmuch-hello-update)
     (define-key map "G" 'notmuch-hello-poll-and-update)
     (define-key map (kbd "<C-tab>") 'widget-backward)

emacs/notmuch-lib.el

@@ -87,6 +87,11 @@ the user hasn't set this variable with the old or new value."
   "Return the user.primary_email value from the notmuch configuration."
   (notmuch-config-get "user.primary_email"))
 
+(defun notmuch-kill-this-buffer ()
+  "Kill the current buffer."
+  (interactive)
+  (kill-buffer (current-buffer)))
+
 ;;
 
 ;; XXX: This should be a generic function in emacs somewhere, not

emacs/notmuch-show.el

@@ -555,7 +555,7 @@ function is used. "
 (defvar notmuch-show-mode-map
       (let ((map (make-sparse-keymap)))
 	(define-key map "?" 'notmuch-help)
-	(define-key map "q" 'kill-this-buffer)
+	(define-key map "q" 'notmuch-kill-this-buffer)
 	(define-key map (kbd "<C-tab>") 'widget-backward)
 	(define-key map (kbd "M-TAB") 'notmuch-show-previous-button)
 	(define-key map (kbd "<backtab>") 'notmuch-show-previous-button)
@@ -1043,7 +1043,7 @@ argument, hide all of the messages."
 	until (not (notmuch-show-goto-message-next)))
   ;; Move to the next item in the search results, if any.
   (let ((parent-buffer notmuch-show-parent-buffer))
-    (kill-this-buffer)
+    (notmuch-kill-this-buffer)
     (if parent-buffer
 	(progn
 	  (switch-to-buffer parent-buffer)

emacs/notmuch.el

@@ -232,7 +232,7 @@ For a mouse binding, return nil."
   "Exit the search buffer, calling any defined continuation function."
   (interactive)
   (let ((continuation notmuch-search-continuation))
-    (kill-this-buffer)
+    (notmuch-kill-this-buffer)
     (when continuation
       (funcall continuation))))
 
@@ -824,7 +824,7 @@ same relative position within the new buffer."
 	(target-thread (notmuch-search-find-thread-id))
 	(query notmuch-search-query-string)
 	(continuation notmuch-search-continuation))
-    (kill-this-buffer)
+    (notmuch-kill-this-buffer)
     (notmuch-search query oldest-first target-thread target-line continuation)
     (goto-char (point-min))))