[GB.TEST]
* OPT: Hide more classes and symbols.
TapPrinter, TapParser and TapContext are not exported anymore. The Tap
constants are moved into other classes. Some public methods/properties
that expose printer, parser or context are hidden.
[GB.TEST]
* BUG: Do not trim whitespace from diagnostic lines.
* NEW: Show TODOs (failed and bonus) and SKIPs in summary.
Previously, TapPrinter.Diagnostic would Trim$ its argument before
splitting it by line. This would remove any indentation that may
be useful for formatted diagnostics output, so it has to go.
Additionally I special-case Null and gb.Lf to print exactly "#\n",
which is a common use case as a visual separator.
