Fix 's' retroflexion on roots
Fix 'n' deletion on e.g. 'ninyiva'
Add support for 6.4.98

But it's overruled because 6.4.77 acts immediately afterward. This
looks like a good place for utsarga-apavada...!
Add support for samprasarana and at-upadha-vrddhi

About 40% of the tests pass.
Add support for 'mAdyati', 'gUhati'
Add better handling of optional rules
Fix inputs to 'tud' test in lat.csv
Change filter API

Filters now accept just a state and an index
Add script for diff check on tests
Add support for 'anadeshadi' in 6.4.120 etc.