Support saving to buffer

[Ten0]

The current bindings only allow to save to a file.
For our use case, we need to parse and remove exif tags in memory, for all kinds of images.
=> We would need to be able to save the resulting images (after removing tags), to a buffer (ideally using Write?).

It looks like this might be possible using https://gitlab.gnome.org/GNOME/gexiv2/-/blob/e4d65b31cd77f28ef248117e161de9d8cc31d712/gexiv2/gexiv2-metadata.cpp#L715 or https://gitlab.gnome.org/GNOME/gexiv2/-/blob/e4d65b31cd77f28ef248117e161de9d8cc31d712/gexiv2/gexiv2-metadata.cpp#L592, but is not currently available through the rust libraries.

[felixc]

That would be fantastically useful! Patches to expose gexiv2_metadata_save_stream (first via gexiv2-sys and then here) would be welcome.

[yzernik]

Anyone working on this? I might give it a try if no one else is.

[felixc]

Please go for it!

[mexicantexan]

@felixc @yzernik Would this work? -> felixc/gexiv2-sys#26