allow skipping of entire subtrees during tree parsing

I normally use dot (wildcard) to jump over uninteresting
nodes/trees in v2, though I'm not sure how well that will work in 3.0 as the
parsing algorithm is a little different. I might have to add another
element other than dot to mean ignore tree instead of just ignore
node. Use ^(ARGS ...) for ARGS node with any number of children. Or
is it ^(ARGS (.)*)? No, that won't traverse its children. Ok, "..."
is an idiom that means don't care in a tree sense. '.' won't be
enough as it means don't care about one node.

I'll have to ask the TreeNodeStream to skip so it can be done efficiently maybe.