Fix for issue 629.

I rearranged the operands in the if statement to avoid possibility of integer overflow, and I fixed the log message to calculate the remaining bytes correctly.  The second chunk of the diff is the important one, the first chunk is for consistency only.  I didn't spot any other code having the same issue.

With this fix, there are no errors in the server log after running the OULU test suites and the server is still accepting requests.