* lisp/subr.el (add-hook): fix typo in doc string.
The optional fourth argument, LOCAL, if non-nil, says to modify
the hook's buffer-local value rather than its global value.
-This makes the hook buffer-local, and it makes t a member of the
+This makes the hook buffer-local, and it makes it a member of the
buffer-local value. That acts as a flag to run the hook
functions of the global value as well as in the local value.