Remove duplicate definition of this_t in pnm format's scanline_reader
Merge branch 'tiff-cmyk' into develop
First bit of getting alpha channels saved in TIFF files. The Extra Samples tag is now set.
Initial implementation of premultiplier, which is used when saving TIFF (since by convention this uses premultiplied alpha)
Allow more complex properties (with more than one element) to be set when saving TIFF.
Merge branch 'tiff-alpha-save' of https://github.com/gallafent/gil into develop