being edited in DrRacket (via places)
Added an API to let tools have access to that
information (and compute more stuff)
Used that to make an online version of Check Syntax
which led to a separately callable Check Syntax API.
Removed "info.rkt", since all entries were unused; switched ".ss" to
".rkt" in both real code and tested code (except for the teachpack
tests); modernized some tests to use symbolic requires (which would also
make it easier to deal with).