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.
- improved the drawing speed in mrlib's graph pasteboard
by caching the background arrows (optionally; only turned
on for the module browser. in redex, this probably won't
speed anything up so it isn't used)
- added a search feature to the module graph to help find
dependencies; type in string and some of the graph changes
color
