PNG_IO SvnCode

Changed the input and output sample types to be discrete rather than modular to permit use of integer subtypes.

Updated references in comments to refer to the relevant section(s) of the ISO standard and not the PNG Spec V1.2 as before.

Changed Image_Handle generic parameters to be unconstrained.

Changed declaration of package version in order to achieve compliance with Ravenscar profile.

Added fourth "&" function to join two Chunk_Lists. Version 4.2.3.

Added fourth "&" function to join two Chunk_Lists.

Added third "&" function for chunks to return a Chunk_List from two Chunks
Changed version to 4.2.2. Fixed bug in function Standard_RGB_Chunk.

Added third "&" function for chunks to return a Chunk_List from two Chunks.
Defined constants for gamma 1 and 2.2.

Changes to the generic PNG Write procedures to permit the Sample type to be matched by modular types as well as signed integer types. Change of PNG_IO version number to 4.2.1.

First version committed to Sourceforge CVS corresponding to release 4.1 of PNG_IO.