checking jit-lock-defer-multiline

[martin rudalics]

The recent change to `jit-lock-fontify-now' may disable checking the
`jit-lock-defer-multiline' property in a number of cases.  It might make
sense to introduce a variable `jit-lock-defer-multiline' with default
nil.  Modes like `perl-mode' would set this to t and the check in
`jit-lock-fontify-now' become:

           (when (and jit-lock-context-unfontify-pos
                      (>= jit-lock-context-unfontify-pos start)
                      (< jit-lock-context-unfontify-pos next)
                      (not jit-lock-defer-multiline))
             (setq jit-lock-context-unfontify-pos next))