As in Idris 1 - if an interface declares a method as total or covering,
then all implementations have to satisfy that.
Temporarily turn off %default directive again, at least until totality
checking works as it should (this is probably better than removing it
from various places because I'll forget to put them back)
This means temporarily removing some '%default total' from the libraries
and tests, since the input for codata checking isn't right yet (it needs
appropriate use of inlining)
Should have done this ages ago, it was much easier than I expected...
this adds an explicit error clause before running the pattern match
compiler for runtime case trees, but only if the coverage checker finds
there are missing cases.
