removal of useless rules via CPP but via `if (0)', so that the
compiler still check the code is valid.
For instance, it should have noticed `rline' no longer exists: use
the `line' member of rule_t.
* src/gram.c (dummy, rline): Remove, unused.
* src/gram.c (dummy): Remove, now there is actual code in gram.c.
(This useless function was defined only to work around VMS linkers
that can't handle compilation units with variables only).
* src/reduce.c (dump_grammar): Use it to trace the construction of
ritem.
