mirax: Drop w/h from struct tile
Drop old TODO
hamamatsu: Migrate NGR ops from ops-ngr
hamamatsu: Rename some variables in hamamatsu_vmu_part2()
hamamatsu: Drop _openslide_ngr
hamamatsu: Rename one_jpeg to jpeg
hamamatsu: Rename tile to jpeg_tile
hamamatsu: Rename level to jpeg_level
hamamatsu: Rename ops
mirax: Simplify src_[xy] handling in read_tile()

src_[xy] is only nonzero if we're subtiling.