BitfieldMan: Rewrite getCompletedLength and countMissingBlockNow

Rewritten so that no memory allocation is required for these
functions.
Fix compile error with i686-w64-mingw32-g++ 4.6

Which does not support constructor delegate
Add countSetBitSlow tests
Use std::unique_ptr instead of array_ptr
Use std::unique_ptr for HttpResponse instead of std::shared_ptr
Use std::unique_ptr for HttpRequest instead of std::shared_ptr
Use std::unique_ptr for StreamFilter instead of std::shared_ptr