[racket-dev] code coverage coloring

A different line of reasoning is this.  DrRacket gives the impression
that coverage is a property of the language selected for a buffer.
That's why if I have two tabs, one in *SL and another in #lang racket,
one has coverage and other does not, without my having to ever touch
the Details panel.  And this would presumably true when *SL is done as
a #lang instead (which I've repeatedly heard it eventually should be).

Shriram