Add reading of YA tiff images
Add reading of YA tiff images

This code does not check that the extra channel is in fact
a transparency channel

Chobbes/Juicy.Pixels,Twinside/Juicy.Pixels,Chobbes/Juicy.Pixels,Twinside/Juicy.Pixels,clinty/Juicy.Pixels,clinty/Juicy.Pixels,Twinside/Juicy.Pixels