TAIL-ANNOTATE used MERGE-TAIL-CALLS policy (which is an integer) as a
boolean, instead of comparing it to zero. Oops. This means that we always did
TCO when possible.
Since adding a debug-catch-tag effectively prevents TCO, and the policy
controlling that looks just like what we would like to have in
MERGE-TAIL-CALLS if TAIL-ANNOTATE were to use it correctly... just deprecate