* src/lparse.ml (lexp_expand_macro): Use `eval-call`.

The main purpose of this is to avoid converting the `sexp list` of args
to a `lexp list` on its way to a `value_type list` since conversion from
lexp to value_type doesn't always create a Vsexp.

* src/builtin.ml (o2l_list): Remove.

* src/lparse.ml (lexp_eval): New function, extracted from lexp_expand_macro.
(lexp_expand_macro): Use it.  Add `loc` argument.  Use `eval_call`.