[CM] s7_define_constant_with_environment useless?

[bil at ccrma.Stanford.EDU]

Thanks for the bug report!  It looks like I forgot
to test the local case; I've added several more
tests to ffitest.c, and now that function is:

s7_pointer s7_define_constant_with_environment(s7_scheme *sc, s7_pointer 
let, const char *name, s7_pointer value)
{
   const s7_pointer sym = make_symbol_with_strlen(sc, name);
   s7_define(sc, T_Let(let), sym, value);
   set_possibly_constant(sym);
   if (let == sc->rootlet)
     {
       set_immutable(sym);
       set_immutable(global_slot(sym));
     }
   else
     {
       s7_pointer slot = symbol_to_local_slot(sc, sym, let);
       set_immutable_slot(slot);
     }
   return(sym);
}