Added temporary file for merging
Removed m_beenSplit and m_bytesTotal
Removed updateRange()
used flush() in File::append()
Added mutex in Range class and found THE BUG

Whenever we started a transaction, we sent a range size.
The transaction now asks for a fixed amount of data.
Meanwhile the range size was changed due to split.
When transaction is ready, it again updated the range size to
the total bytes it had requsted and hence THE BUG was conceived.