We need to split these steps up in preparation for multi-core
support. Reading needs to be done in a serial manner, whilst
decoding can be done in parallel.
This also involved a rather large cleanup of the Tight decoder.
Use PixelBuffer objects as the interface for encoders and decoders
This avoid a lot of unnecessary middle men. This also pushes the
responsibility for pixel format conversion into the encoders and
decoders. The new bufferFromBuffer() is used for direct conversion,
rather than PixelTransformer/TransImageGetter.
min and max changed to vncmin and vncmax. This solves many problems: Some platforms predefines or redefines these symbols. Some platforms have header files which chokes if min or max are defined.