Log Message:
Update JHead to version 2.84 in order to fix CVE-2008-4575 (buffer overflow).
Changes since old version 2.4:

 - Fix -da option.
 - Removed some debug printf which were accidentally left in.
 - Avoid duplicating exif header on some commands.
 - Fix up return codes.
 - Preserve file permissions and time when files are modified.
 - Read ISO euqivalnt and white balance from canon makernote.
 - Added -rt (replace thumbnail) feature, and rotate the thumbnail also
   when using the -autorot feature.
 - Added -rgt (regenerate thumbnail) feature.
 - Added -orp and -orl options.
 - Fix typecast issue run itno with GCC 4.
 - Fix shutter speed display in '-c' mode for very long shutter speeds.
 - Fix some nitpicks from Debian folks.
 - Fix a bug in autorot when rotating filenames with spaces in them.
 - Improved handling of corrupt exif linkages in exif header.
 - Added -a (rename associated files) options.
 - Remove maximum jpeg sections limit.
 - Added -ds option.
 - On clearing rotation, clear the image and the optinoal thumbnail rotation
   tags (some viewers use the wrong tag).
 - Add -mkexif option to make a new exif header.
 - Added IPTC handling.
 - Added -q option.
 - Fix handling of corrupted GPS directory.
 - Extract focus distance from canon makernote.
 - Extract subject range (pentax and fuji cameras).
 - Fix it so it no longer deletex XMP sections.
 - Improve IPTC handling a little.
 - Change how date is encoded with -mkexif section to make it more compatible.
 - Make jhead aware of XMP data and not delete it.
 - Decode more exif tags for '-v' mode.
 - Fix a bunch of potential string overflows.
 - Fix bug where IPTC sction was not deleted by -purejpg.
 - Fix GPS altitude decode bug.