tor/changes/bug21290

  o Minor bugfixes (configure, autoconf):
    - Rename the configure option --enable-expensive-hardening to
      --enable-fragile-hardening. TROVE-2017-001 was triggerable only through
      the expensive hardening which is making the tor daemon abort when the
      issue is detected. Thus, it makes tor more at risk of remote crashes but
      safer against RCE or heartbleed bug category. Fixes bug 21290; bugfix on
      0.2.5.4-alpha.