recompiling with compile environments, fluid languages, cleanups

* ice-9/boot-9.scm (compile-time-environment): Remove definition from
  boot-9 -- instead, autoload it and `compile' from (system base
  compile).

* libguile/objcodes.h:
* libguile/objcodes.c (scm_objcode_to_program): Add an optional argument,
  `external', the external list to set on the returned program.

* libguile/vm-i-system.c (externals): New instruction, returns the
  external list. Only used by (compile-time-environment).

* libguile/vm.c (scm_load_compiled_with_vm): Adapt to
  scm_objcode_to_program change.

* module/language/scheme/translate.scm (translate): Actually pay
  attention to the environment passed as an argument.
  (custom-transformer-table): Expand out (compile-time-environment) to
  something that can be passed to `compile'.

* module/system/base/compile.scm (*current-language*): Instead of
  hard-coding `scheme' in various places, use a current language fluid,
  initialized to `scheme'.
  (compile-file, load-source-file): Adapt to *current-language*.
  (load-source-file): Ada
  (scheme-eval): Removed, no one used this.
  (compiled-file-name): Don't hard-code "scm" and "go"; instead use the
  %load-extensions and %load-compiled-extensions.
  (cenv-module, cenv-ghil-env, cenv-externals): Some accessors for
  compile-time environments.
  (compile-time-environment): Here we define (compile-time-environment)
  to something that will return #f; the compiler however produces
  different code as noted above.
  (compile): New function, compiles an expression into a thunk, then runs
  the thunk to get the value. Useful for procedures. The optional second
  argument can be either a module or a compile-time-environment; in the
  latter case, we can recompile even with lexical bindings.
  (compile-in): If the env specifies a module, set that module for the
  duration of the compilation.

* module/system/base/syntax.scm (%compute-initargs): Fix a bug where the
  default value for a field would always replace a user-supplied value.
  Whoops.

* module/system/il/ghil.scm (ghil-env-dereify): New function, takes the
  result of ghil-env-reify and turns it back into a GHIL environment.

* scripts/compile (compile): Remove some of the tricky error handling, as
  the library procedures handle this for us.

* test-suite/tests/compiler.test: Add a test for the dynamic compilation
  bits.

scripts/compile

@@ -71,20 +71,6 @@ Report bugs to <guile-user@gnu.org>.~%")
                                 (if expand-only? '(#:e) '())
                                 (if translate-only? '(#:t) '())
                                 (if compile-only? '(#:c) '()))))
-
-      (catch #t
-             (lambda ()
-               (for-each (lambda (file)
-                           (apply compile-file file compile-opts))
-                         (option-ref options '() '())))
-             (lambda (key . args)
-               (format (current-error-port) "exception `~a' caught~a~%" key
-                       (if (null? args) ""
-                           (if (string? (car args))
-                               (string-append " in subr `" (car args) "'")
-                               "")))
-
-               (format (current-error-port) "removing compiled files due to errors~%")
-               (false-if-exception
-                (for-each unlink (map compiled-file-name files)))
-               (exit 1))))))
+      (for-each (lambda (file)
+                  (apply compile-file file compile-opts))
+                (option-ref options '() '())))))