[racket-dev] online check syntax: now disabled by default

I've disabled the online check syntax by default because I'm worried
about stability issues (and deadlock issues, but those just keep
online check syntax from working, not so much drracket itself). So
I'll probably leave it off for the next release but I encourage you to
turn it back on try it out and report if you run into problems. You
can turn it on by clicking on the little red dot in the bottom right
corner of the drracket window.

Thanks,
Robby