Don't require font-lock any more.

Don't require font-lock any more.
(jit-lock-functions): Make buffer-local.
(jit-lock-saved-fontify-buffer-function): Remove.
(jit-lock-mode): Remove autoload cookie.
Remove font-lock specific code.
(jit-lock-unregister): Don't bother handling complex hooks any more.
(jit-lock-refontify): New function.
(jit-lock-fontify-buffer): Use it.
(jit-lock-function-1): Replaced by jit-lock-fontify-now.
(jit-lock-fontify-now): Renamed from jit-lock-function-1.
Add optional args START and END.
Never call font-lock-fontify-region directly.
(jit-lock-function, jit-lock-stealth-fontify): Use it.