This is an initial import of exiv2 (0.7,
http://home.arcor.de/ahuggel/exiv2) into libextractor.

The current code has the following issues:

* more memory leaks than the rest of LE combined and squared,
  thus cannot be added by default
* previously generated header file is used (exv_conf.h),
  should be merged with Extractor's config.h where needed;
  unnecessary or bad checks should be eliminated
* lots of dead code
* possibly contains code that prints to stdout/stderr
* not sure if the parser is robust enough (needs testing)

