runtests: Add support for dump-only tests
Add enum test
dustmite: Add --dump-html
runtests fixup
splitter: Reimplement pairs like any other separators

This allows them to have priority, like other separators,
which fixes certain situations. This also simplifies code and
makes splitting work more like older DustMite versions.
splitter: Recognize function invariants
splitter: Tweak pairing postprocessor
splitter: Tweak block keyword postprocessor

Note: this introduces a test regression (merge).
splitter: Tweak block statement postprocessor

This fixes the regression introduced in the previous commit.
dustmite: Add --strategy switch
dustmite: Autoretry cache writes

Apparently, it is actually likely for two Dustmite instances,
running on a RAM drive, to attempt to write the same cache result
simultaneously.
Add pingpong strategy
Add inbreadth strategy
dustmite: Change default strategy to inbreadth
dustmite: Improve "else" handling