* symbols.c (scm_sysintern): Renamed to

* symbols.c (scm_sysintern): Renamed to
scm_sysintern_no_module_lookup.
(scm_sysintern): New function to take the place of the old
scm_sysintern. It uses the current toplevel lookup closure to give
the symbol its value.  This is a temporary hack to put packages
like gtcltk into their own module.
(scm_can_use_top_level_lookup_closure_var): New variable to tell
us whether `scm_top_level_lookup_closure_var' has been initialized
and is usable.
* eval.c (scm_init_eval): Set it.