remove compile-time-environment

* module/ice-9/boot-9.scm (guile-user): Move the `compile' autoload to
  the guile-user module. Remove reference to compile-time-environment.

* module/language/scheme/compile-ghil.scm:
* module/language/tree-il/compile-glil.scm:
* module/language/tree-il/optimize.scm:
* module/system/base/compile.scm:
* test-suite/tests/compiler.test: Remove definition of and references to
  compile-time-environment. While I do think that recompilation based on
  a lexical environment can be useful, I think it needs to be implemented
  differently. So for now we've lost nothing if we take it away, as it
  doesn't work with syncase anyway.

module/language/scheme/compile-ghil.scm

@@ -414,16 +414,6 @@
   (,args
    (-> (values (map retrans args)))))
 
-(define-scheme-translator compile-time-environment
-  ;; (compile-time-environment)
-  ;; => (MODULE LEXICALS . EXTERNALS)
-  (()
-   (-> (inline 'cons
-               (list (retrans '(current-module))
-                     (-> (inline 'cons
-                                 (list (-> (reified-env))
-                                       (-> (inline 'externals '()))))))))))
-
 (define (lookup-apply-transformer proc)
   (cond ((eq? proc values)
          (lambda (e l args)