tiffdump: Consolidate byte order code in a helper function
tiffdump: Consolidate read_tiff_tag functions
tiffdump: Consolidate TIFF type getters
tiffdump: Consolidate read_uint functions
tiffdump: Make internal data structures private
tiffdump: Replace hash_key_helper with g_hash_table_get_keys()
tiffdump: Avoid separate allocations for directory keys
tiffdump: Track directories using GPtrArray instead of GSList
tiffdump: Drop item argument to print_tag()
tiffdump: Rename _openslide_tiffdump_item to tiff_item
tiffdump: Rename read_tiff_tag()
tiffdump: Update field widths for BigTIFF
tiffdump: Support BigTIFF
tiffdump: Consolidate read_tiff_value() calls
tiffdump: Only include tiff.h, not tiffio.h
tiffdump: Avoid asserting in accessors

The only way for a vendor backend to find out what's in the TIFF
directories is to try accessing them.
Rename tiffdump to decode-tifflike
hamamatsu: Allow JPEGs to start at non-zero file offsets

Needed for NDPI.  Effectively reverts 8ef253b7.
hamamatsu: Rename some things that will be used for NDPI
hamamatsu: Move JPEG ops initialization to a helper function