PNG_IO SvnCode

Removed use of buffer in writing a file, using on-the-fly compression of data instead.

Fixed an error in a comment.

Added a compression level parameter to the write procedures to permit user control over the Zlib compression level. Moved the with clause for Zlib to the spec in order to provide renamings of some Zlib types etc.

Added a compression level parameter to permit user control over the Zlib compression level.

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.