(which-func-format): Remove spurious space.

(which-func-format): Remove spurious space.
(which-func-mode): Don't make it permanent-local.
(which-func-ff-hook): Allow which-func-maxout to be nil.
(which-func-update): Simplify a bit.  Only run if which-func-mode is t.
(which-func-mode): Simplify.
Use post-command-idle-hook rather than post-command-hook.
Go through all buffers and update their state.
(which-function): Also try add-log-current-defun-function.