Since lots of testing modules test themselves by looking at the formatted output, didn't have a lot of choice, any change to the format breaks their tests.

To mitigate this, we can provide a legacy TAP formatter which has all the quirks of the 0.9x formatter. It will be used by default by Test::Builder::Tester and instructions provided for non TBT tests to switch over to it.

This will provide a smooth upgrade path. TBT modules will need no change. Others will simply need to change the formatter conditional on the version of Test::Builder.