run-in-thread accepts a new optional argument: nolock.

run-in-thread accepts a new optional argument: nolock.

When it is no-nil the thread does not try to get a lock on the current
buffer before work on it.

With this change, the following example works quite smoothly; while
loading imap folders, gnus yields to another thread:

(load-library "gnus")

;; Redefine to use yield
(defun imap-send-command-wait (command &optional buffer)
 (imap-wait-for-tag (prog1 (imap-send-command command buffer) (yield)) buffer))

(progn
 (run-in-thread '(gnus) t)
 (dotimes (i 20)
   ;; yield is called automatically during a buffer-switch
   (message (format "I got here %i" i))))