Provide a JavadocTester method for non-overlapping, unordered output matching

Here's a use case. Consider errors being reported out of order with respect to the their source lines. Consider also that the test doesn't want to hardcode those line numbers and wants to make sure that the errors are found at least once.

The functionality described in the above use case is somewhat similar to that of java.util.Collection#containsAll. I don't think any of methods such as checkOutput, checkUnique, or prospective checkOrder(...Output...) would do.