o Minor bugfixes:
    - In the function munge_extrainfo_into_routerinfo(), check the return
      value of memchr(). This would have been a serious issue if we ever
      passed a non-extrainfo to munge_extrainfo_into_routerinfo. Fixes
      bug 8791; bugfix on 0.2.0.6-alpha. Patch from Arlo Breault.