Variable: jit-lock-after-change-extend-region-functions

Hook that can extend the text to refontify after a change.
This is run after every buffer change. The functions are called with
the three arguments of `after-change-functions': START END OLD-LEN.
The extended region to refontify is returned indirectly by modifying
the variables `jit-lock-start' and `jit-lock-end'.

Note that extending the region this way is not strictly necessary, except
that the nature of the redisplay code tends to otherwise leave some of
the rehighlighted text displayed with the old highlight until the next
redisplay (see comment about repeated redisplay in `jit-lock-fontify-now').