Implement `local-eval', `local-compile', and `the-environment'

Implement `local-eval', `local-compile', and `the-environment'

* module/ice-9/local-eval.scm: New module (ice-9 local-eval) which
  exports `the-environment', `local-eval', and `local-compile'.

* libguile/debug.c (scm_local_eval): New C function that calls the
  Scheme implementation of `local-eval' in (ice-9 local-eval).

* libguile/debug.h (scm_local_eval): Add prototype.

* doc/ref/api-evaluation.texi (Local Evaluation): Add documentation.

* test-suite/tests/eval.test (local evaluation): Add tests.

* test-suite/standalone/test-loose-ends.c (test_scm_local_eval):
  Add test.

* module/Makefile.am: Add ice-9/local-eval.scm.

Based on a patch by Mark H Weaver <mhw@netris.org>.