Support for multiple scans

[ImpulseAdventure]

If multiple components are defined in SOF, then the code expects the same number of components to be identified in the first SOS. Apparently, it is possible to have image components spread over multiple SOS (Scan) segments. The decoder currently assumes that all components should exist in the first scan, leading to table lookup issues and improper decode.

Reported by Alex on 05/05/2011 on http://www.impulseadventure.com/photo/jpeg-snoop.html

([2011-05-05] Imported from https://sourceforge.net/p/jpegsnoop/bugs/5/)

[ImpulseAdventure]

[2011-05-05] Example of image with SOF=3 comps but 3 separate SOS

-- [2014-06-22] Code has now been rewritten to process first scan of image (upcoming release 1.6.7), though it still cannot merge decoding of multiple scans into one frame.