Saving TIFF stack does not support tags with type long8

[stilley2]

Title pretty much says it all.

I believe the problem is that this list doesn't contain long8: here

to reproduce

import numpy as np
import PIL
from PIL.TiffImagePlugin import ImageFileDirectory_v2
x = np.ones((2, 10, 10))
pilimgs = [PIL.Image.fromarray(i) for i in x]
ifd = ImageFileDirectory_v2()
ifd[256] = 10
ifd[257] = 10
ifd[65000] = 1234
ifd.tagtype[65000] = 16
pilimgs[0].save("testimgs.tif", save_all=True, tiffinfo=ifd,
                append_images=pilimgs[1:], format="tiff")

[radarhere]

I've created PR #7078 to resolve this.