(I think that the change to `teachpack/htdp/dir' is fine too, looks like
the previous code is dealing with the old restriction of not requiring a
binding that conflicts with the language bindings.)
* Another big chunk of v4-require-isms
* Allow `#lang framework/keybinding-lang' for keybinding files
* Move hierlist sources into "mrlib/hierlist", leave stub behind
svn: r10689
