* Switch srfi/1 and a few other packages (and optionals.ss) to
scheme/base
* Make srfi/1 etc reprovide `filter' from scheme/private/list
* Organize a few modules that were unnecessarily providing a full
language.
* srfi/45 reprovides stuff from scheme/promise (see comments in
"srfi/45/lazy.ss")
svn: r8999
