Remove MallocStrategy/FixedLengthVector vector'd

* Remove MallocStrategy, which was a remnant of olden times anyway
* Clean up FLV to be based on std::vector and thusly avoid weird (and
  incorrect) reallocation logic and partial thread safety in favor of
  no thread safety. (Use ConcurrentFixedLengthVector for such feats)
Merge pull request #290 from bastih/master

Remove MallocStrategy/FixedLengthVector vector'd