[plt-dev] replacement for *-identifier-mapping

I've adapted the code from syntax/boundmap to use the new v4-style names 
(get->ref, put!->set!, etc) and support the new dict interface (in 
scheme/dict), including both mutable and immutable variants. I'd like to 
add it as a new module in the syntax collection.

I'm looking for opinions about noun phrases to replace 
'identifier-mapping'. I'd prefer something shorter.

The module name: syntax/<noun>
Constructors: make-bound-<noun>, make-immutable-bound-<noun>,
   make-free-<noun>, make-immutable-free-<noun>
Lookup: bound-<noun>-ref, free-<noun>-ref
Update: bound-<noun>-set!, free-<noun>-set!
and so on

Here are some that I've thought of:

id-table
id-hash

Thoughts?

Ryan