This was implicit in the `define-block' implementation because of the
conversion from `<foo>' to `$foo$', but that's no longer the case.
This is just a simple, temporary implementation, so don't be alarmed.
* build-aux/bootstrap/libprebirth.js: Updated header documentation to
mention `$$' prefix.
($$js$console): Renamed from `js$console'.
* build-aux/bootstrap/prebirth.js
(_idFromName): Add `global' parameter to add `$$' prefix to generated
identifiers.
(_cdfn, _sexpToEs): Use it.
Mike Gerwitz