fix a small bug in a comment
[bugfix] wrong external representation for syntax type
[bugfix] wrong error message
compare is allowed to take non-symbol values
[bugfix] macroexpand may return a non-symbol value even if passed a symbol.
don't rename each symbol more than a time
Types that can be passed to the rename procedure is only a symbol
er-macro-transformer is no longer defined using sc
er macro no longer requires identifier? defined