Refactor TIFF decoding

[bradh]

This is an initial rework of the TIFF decoder support, in preparation for reading other data types and higher bit depths.

Because this code is starting to get tricky, I really wanted unit tests. Also, this is looking like code that would be useful in general - not just for the specific examples. In support of that, I've made it into a library - notionally libheifio, but I'm flexible on the name. It doesn't get provided as API yet. It has error handling, not just exit() calls.

Resolves #1300

Also resolves a failure reading RGBA planar files.

./examples/heif-enc ~/rgba_planar.tif out.heif
munmap_chunk(): invalid pointer
Aborted (core dumped)

[bradh]

It looks like the library may not be static. That needs to be fixed.

[farindk]

Is this still a draft or ready for merging?

[bradh]

@farindk if you are OK with the design then I am OK with this as an initial implementation that we can build onto.

[farindk]

@farindk if you are OK with the design then I am OK with this as an initial implementation that we can build onto.

Yes, I can merge this and then I would reorganize the files a bit: move the heifio directory next to the libheif directory and move the tests into a subdirectory of the top-level tests directory. Hope that is ok.

[farindk]

Merged with rebase.