libexif: upgrade 0.6.23 -> 0.6.24

libexif-0.6.24 Changelog:

Translation updates: sr, vi, pl, uk, french
fixed regression in exif_data_load_data which could not load EXIF in JPEG data anymore
Decode lots of Canon tag names
removed empty strings from translation (empty string would translate to the PO info header)
various warning removals and code improvements
added sample "persistent" afl fuzzer (100x faster than normal afl fuzzer)

Signed-off-by: Wang Mingyu <wangmy@fujitsu.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>