repeat should return an enumerator when called without a block

[bfoz]

No description provided.

[bfoz]

Now it returns an standard Enumerator, which works well enough, but it could be better with an Enumerator-subclass (Repeater?). A custom subclass would be able to keep the syntax closer to the normal repeat command syntax (no need to use 'each', or to provide a block with non-zero arity).