GitLab

Aside from moving blocks around and adding comments, decisions about numcomponents use switch/case statements to allow CMYK support in the future.
Split out (some of the) Huffman decoding to allow arithmetic support in the future.
Moved memcpy() and memset() into CSupport.
Tested in all colour depths with 1x1; 1x2; 2x1; 2x2 sampling & ChangeFSI.
Tighten up check on cinfo being NULL (was previously only checked in the colour decoder, not the monochrome).

Version 1.37. Tagged as 'SprExtend-1_37'