`PrintWriter::CollectString` and `PrintWriter::CollectStreams` probably need to have a size check

[davidhewitt]

I think it would be possible for an infinite loop which repeatedly prints to OOM the monty host; we should add (optional?) limits to CollectString and CollectStreams and check on each write that we don't exceed these.

[samuelcolvin]

yes. We should probably do it before the bounty program.