This warning checks for functions whose specs include extra types which
the function does not actually return.

This warning checks for functions which return values which are not
included in their specified return type.

This warning checks for underspecified functions, i.e. functions whose
specifications are strictly more permissive than their success typing.

This warning checks for unmatched returns, i.e., for exhaustiveness on
structured return values (but not unions of just atoms or integers).

* ray/dialyzer-error-handling:
  dialyzer: enable -Werror_handling

* ray/dialyzer-extra-return:
  dialyzer: enable -Wextra_return

* ray/dialyzer-missing-return:
  dialyzer: enable -Wmissing_return

* ray/dialyzer-underspecs:
  dialyzer: enable -Wunderspecs

* ray/dialyzer-unmatched-returns:
  dialyzer: enable -Wunmatched_returns