(copy_at, copy_dollar): Instead of outputting the hard coded
values of $$, $n and so forth, output invocation to b4_lhs_value,
b4_lhs_location, b4_rhs_value, and b4_rhs_location.
+ Note: this patch partially drops `semantic-parser' support: it
+ always does `rule_length - n', where semantic parsers ought to
+ always use `-n'.
* data/bison.simple, data/bison.c++ (b4_lhs_value)
(b4_lhs_location, b4_rhs_value, and b4_rhs_location: New.