Move `error` from top_stmts and top_stmt to stmt

By this change, syntax error is recovered smaller units.
In the case below, "DEFN :bar" is same level with "CLASS :Foo"
now.

```
module Z
  class Foo
    foo.
  end

  def bar
  end
end
```

[Feature #19013]

1 files changed, 1 insertions, 0 deletions

diff --git a/ext/objspace/objspace.c b/ext/objspace/objspace.c
index 0b1b094325..ca08604c95 100644
--- a/ext/objspace/objspace.c
+++ b/ext/objspace/objspace.c
@@ -493,6 +493,7 @@ count_nodes(int argc, VALUE *argv, VALUE os)
                 COUNT_NODE(NODE_ARYPTN);
                 COUNT_NODE(NODE_FNDPTN);
                 COUNT_NODE(NODE_HSHPTN);
+                COUNT_NODE(NODE_ERROR);
 #undef COUNT_NODE
               case NODE_LAST: break;
             }