remove compile-time-environment

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.