For each length 'n' bytes, this counts the number of pages which, when prefixes
of length >= n (within the sequence shown below) are passed through jchardet,
consistently give the same answer (including 'unknown' as a valid answer) as
when the entire document is passed through.

Pages: 126989

Bytes       Pages       (Difference)
512     77.8%   98852
1024    80.2%   101870  (+ 3018)
1536    81.4%   103397  (+ 1527)
2048    82.4%   104608  (+ 1211)
2560    83.2%   105657  (+ 1049)
3072    84.0%   106649  (+ 992)
3584    84.7%   107575  (+ 926)
4096    85.4%   108409  (+ 834)
8192    88.4%   112222  (+ 3813)
16384   91.0%   115508  (+ 3286)
32768   92.1%   116981  (+ 1473)
65536   92.4%   117389  (+ 408)
(more)  96.5%   122534  (+ 5145)