Font-lock in COMINT modes

[JD Smith]

In Emacs 22, my idlwave-shell mode font-lock fontifies
comments/strings/etc. without having been asked to. This can be
problematic if you miss a closing quote, and all subsequent text gets
string fontification.  In Emacs 21, the only fontification was comint
coloring the prompt blue.

I don't mind the fontification so much (in fact I like it), it's just
that missing string quotes allow it to run away, latching onto parts
of the subsequent input and output in a way that's hard to cancel.
Perhaps there is an easy way to inhibit scanning through the prompt?

JD