Merge from 6.x to 7.x branch.
Merge include update for following issues (6.x branch) :

CHANGES LOG
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2010/04/27
* UTF-8 support #783310 by silvio
* http://drupal.org/node/783344 : XMP Support by silvio

2009/12/01
* added option to choose if the exif information should be refreshed upon update or not
Merged.

2009/11/25
* Prevent from reading exif information from png files (http://drupal.org/node/613776) by rapsli

2009/10/26
* Multiple IPTC Keywords http://drupal.org/node/226703 by chachasikes
* Error with exif extraction http://drupal.org/node/473140 by raintonr

2009/09/24 dman
* Cleaned up PHP E_ALL notices (undefined variables) in a few places, including exif.class
* Typo in exif_nodeapi()
* http://drupal.org/node/473140 : Applied fix for array-structured Geo tags 

2009/09/24
* Applied Drupal Code styles

2009/09/21
* http://drupal.org/node/588528 : Better communications for users who don't have the exif_read_data function available
