* boot-9.scm (beautify-user-module!): Beautify also if public

* boot-9.scm (beautify-user-module!): Beautify also if public
interface is set to the module itself.  In this way we can use
beautify-user-module! to beautify a module prepared for object
code.
(process-define-module): Special case: Try to load object code as
well if a module does :use-module on itself.
* boot-9.scm: Bugfix: Since boot-9.scm is now loaded from
invoke_main_func, we can no longer be sure that all modules have
been registered when boot-9.scm is loaded.
(register-modules): New function: Register and tag modules
registered by scm_register_module_xxx since last call to this
function.  Modules are tagged with the dynamic object passed as
argument.  (Already linked modules should be tagged with #f.)
(init-dynamic-module, link-dynamic-module): Call register-modules
first to register linked modules.
* boot-9.scm (init-dynamic-module): Remove module from
registered-modules as soon as possible in case we are recursively
invoked; Set public interface before doing the dynamic-call.
* boot-9.scm (map-in-order): Removed (replaced by scm_serial_map).
(abort-hook, before-error-hook, after-error-hook,
before-backtrace-hook, after-backtrace-hook, before-read-hook,
after-read-hook, exit-hook): Make hooks with `make-hook'.
* boot-9.scm: Make hooks first class citizens and make them easier
to use from C:
(make-hook, add-hook!, remove-hook!, run-hooks): Moved to
libguile/feature.c.
* boot-9.scm: Added warnings about bindings used in
libguile/modules.c: the-module, set-current-module,
make-modules-in, beautify-user-module!, module-eval-closure.