* modules.c (scm_module_type): New.

* modules.c (scm_module_type): New.
(scm_post_boot_init_modules): Initialize from Scheme value.
(the_module, scm_current_module, scm_init_modules): the_module is
now a C only fluid.
(scm_current_module): Export to Scheme.
(scm_set_current_module): Do not call out to Scheme, do all the
work in C.  Export procedure to Scheme.  Only accept modules, `#f'
is no longer valid as the current module.  Only set
scm_top_level_lookup_closure_var and scm_system_transformer when
they are not deprecated.
(scm_module_transformer, scm_current_module_transformer): New.

* modules.h (scm_module_index_transformer, SCM_MODULE_TRANSFORMER,
scm_current_module_transformer, scm_module_transformer): New.