scm_is_eq for SCM vals, not == or !=

scm_is_eq for SCM vals, not == or !=

* libguile/bytevectors.c (scm_make_bytevector, STRING_TO_UTF)
  (UTF_TO_STRING):
* libguile/continuations.c (scm_i_check_continuation):
* libguile/expand.h (SCM_EXPANDED_P):
* libguile/fluids.c (scm_i_make_with_fluids):
* libguile/generalized-vectors.c (scm_make_generalized_vector):
* libguile/goops.c (SCM_GOOPS_UNBOUNDP, slot_definition_using_name):
  (scm_c_extend_primitive_generic, more_specificp, scm_make)
* libguile/i18n.c (SCM_VALIDATE_OPTIONAL_LOCALE_COPY):
  (scm_locale_string_to_integer)
* libguile/modules.c (resolve_duplicate_binding):
  (scm_module_reverse_lookup)
* libguile/posix.c (scm_to_resource):
* libguile/r6rs-ports.c (scm_put_bytevector):
* libguile/socket.c (scm_connect, scm_bind, scm_sendto
* libguile/stacks.c (find_prompt):
* libguile/variable.c (scm_variable_ref, scm_variable_bound_p):
* libguile/vm-engine.h (ASSERT_BOUND_VARIABLE, ASSERT_BOUND)
* libguile/vm-i-system.c (VARIABLE_BOUNDP, local_bound)
  (long_local_bound, fluid_ref): Use scm_is_eq to compare, not == / !=.