o Major bugfixes (security):
    - Downgrade the "-ftrapv" option from "always on" to "only on when
      --enable-expensive-hardening is provided."  This hardening option, like
      others, can turn survivable bugs into crashes--and having it on by
      default made a (relatively harmless) integer overflow bug into a
      denial-of-service bug. Fixes bug 21278 (TROVE-2017-001); bugfix on
      0.2.9.1-alpha.