tor/changes/memarea_overflow

  o Minor bugfixes (pointer arithmetic):
    - Fix a bug in memarea_alloc() that could have resulted in remote heap
      write access, if Tor had ever passed an unchecked size to
      memarea_alloc().  Fortunately, all the sizes we pass to memarea_alloc()
      are pre-checked to be less than 128 kilobytes. Fixes bug 19150; bugfix
      on 0.2.1.1-alpha. Bug found by Guido Vranken.