tiff: Rearrange some code
tiff: Abstract handle cache out of TIFF ops data
tiff: Pass only tile col/row to tilereader
tiff: Add utility function to read raw tile data
aperio: Use CLAMP() in write_pixel_ycbcr()
aperio: Drop some arguments to copy_aperio_tile()
Makefile: Clean up file lists
Move JPEG 2000 support into its own file
hash: Add API for invalidating a hash
Move TIFF hashing into tiff
tiff: Fix wild pointer dereference in openslide_can_open()
tiff: Provide API for setting properties and calculating hash
tiff: Move border clipping into helper function
tiff: Use tile coordinates in cache key
tiff: Drop some members from tiff_level
tiff: Rename generic tilereader
tiff: Change _openslide_tiff_read_tile_data argument order

for consistency.
tiff: Fold _paint_region() into caller
trestle: Copy and paste relevant part of TIFF ops

Drop dependency on _openslide_add_tiff_ops() by copying its
implementation from ops-tiff.
trestle: Drop unnecessary arguments