Make heterogenous vector typechecking not double typecheck the arguments.
Change tc-app-lambda to not return bad filters.

Makes tc/rec-lambda/check return the actual results, and erase the names of
the values bound by the let.
Make tc-values not misuse expected.
Make wcm not misuse the expected results.
Fix expected use in single-value.
Fix tc-if. Remove dead cases and misuse of expected.
Fix misuse of expected in tc-send.