implement Array.prototype.toString and a test for it.  seems to just call .join on this.
pretty big error cleanup, especially wrt toString and console.log.  also creating errors gives them the right specops now.
correct exception text
make the closureenv functions take actual integer constants instead of creating an ejsval for these args (which was very stupid and eats stack slots.)  also, fix a subtle bug in the SubstituteVariables pass when a parent environment had a closed-over id of the same name as a local mapping.  Move the 'free' function and friends inside ComputeFree, and disable the breaking check-free test for the time being.