* build-aux/bootstrap/rebirth.scm: Provide env to `rebirth->ecmascript-prog'.
(rebirth->ecmascript-prog)[env-es]: New param. Use for `_env' in
generated self-executing ES function.
(es:empty-env): New procedure.
* build-aux/bootstrap/rebirth/es.scm (es:raw): Remove unused macro.
(es:envf)[env]: New parameter. Use in place of hard-coded inherited env.
(es:inherit-env): New procedure, extracted from proceeding.
(lambda, let): Use it.
(null-environment, eval): New procedures.
It's nice being able to do this now.
This starts to pave the path toward ultimately sharing code with Ulambda.
* build-aux/bootstrap/rebirth.scm: Extract steps 0--2 into separate source
files.
* build-aux/bootstrap/rebirth/es.scm: New file containing step 2.
* build-aux/bootstrap/rebirth/macro.scm: New file containing step 1.
* build-aux/bootstrap/rebirth/relibprebirth.scm: New file contaiing step 0.