mirax: Fix GError pile-up on unknown associated image format
test: Add miscellaneous vendor test cases
Add Ventana test cases
mirax: Fix a use of GError for an internal error
ventana: Add level_count assertion

ventana_detect() should already have ensured that we have some levels,
but it doesn't hurt to check.
hamamatsu: Report find_next_ff_marker() errors via GError
test: Rename hamamatsu-vms-jpeg-bad
hamamatsu: Add detail to error messages
hamamatsu: Check for thread errors under JPEG marker debugging
hamamatsu: Fix assertion on premature JPEG EOI

_compute_mcu_start() was improperly returning success in this case.
hamamatsu: Return error from find_bitstream_start() if SOF not found

rather than leaving an out-argument uninitialized.
hamamatsu: Rename verify_jpeg()

It only looks at the JPEG header, and returns several header fields in
addition to verifying.
hamamatsu: Drop redundant find_bitstream_start() call

Save the sof_position and header_stop_position obtained during
validate_jpeg_header() so they don't have to be calculated again during
the first call to _compute_mcu_start().
hamamatsu: Drop unnecessary compute_mcu_start out-params
Drop some unnecessary JPEG casts
hamamatsu: Pass correct size freeing JPEG rows after decode error
jpeg: Allocate row buffers with slice allocator
Add Hamamatsu test cases