[jhc] darcs patch: Cache scoping info, avoid unnecessary maps. (and 2 more)

Tue Feb 19 16:14:10 CET 2008 Lemmih * Cache scoping info, avoid unnecessary maps. Tue Feb 19 16:15:54 CET 2008 Lemmih * Remove debug code. Wed Feb 20 19:40:27 CET 2008 Lemmih * Add a comment describing the function of E.Subst.