follow-up r86169 - 2 minor issues found while writing unit tests

follow-up r86169 - 2 minor issues found while writing unit tests

# Some really obscure Exif properties did not have the Exif byte order taken into account
  and were being extracted with the bytes reversed (for example user comment when encoded as utf-16).
  Not a major issue as these properties are very rare in practise, but certainly not a good thing.
  ( One would think php's exif support would take care of that, but no it does not...)
# Change the fallback encoding for Gif comments to be windows-1252 instead of iso 8859-1. More
  to be consitent with jpg and iptc then anything else.