Allow linebreak/indent in destructured for variable

[helixbass]

@GeoffreyBooth I ran into this when running the Prettier plugin against the Coffeescript codebase:

Things like this (with linebreaks inside the destructured variable of a for loop) currently aren't parsing:

for {
  something,
  somethingElse
}, y in z
  d

The grammar is already set up to accept this, it was just an issue of extending the logic for tagging tokens as eg FORIN

[helixbass]

There was existing logic to "continue the for line" in the case of a backslash line continuer, so just extended that logic to additionally continue the for line (ie preserve @seenFor) if the linebreak is occurring inside a pair of delimiters ie {/} or [/] (as indicated by something having been pushed onto @ends since we saw the FOR token)