#2 Making this code thread safe

[Mark Griffiths]

This is really some awesome code - I've actually been using a Delphi adaptation of it with great success. Unfortunately, the original version wasn't thread safe, so I've modified the Delphi version to make it fully thread safe:

http://www.marktg.com/jpegdec

I've just taken a look at the original assembler and it appears that it also has the same problem, so it might be worth backporting my changes so that anyone else wanting to use this specific library is able to make full use of modern multicore CPUs!