minor tidy
making sure test does not see user's .dataprinter
making sure tests don't see .dataprinter
giving credit where it is due (Changelog update)
removed (broken) support for Digest::Haval256

Turns out Digest::Haval256 support has been broken all the time.
Objects from this class can't really be observed without damaging
the original data. It didn't affect a lot of people since it's an
old module and doesn't even work on 64 bits (though there is a patch
available). If future versions provide a clone() function, it can
be added again.
removing Digest::Haval256 from Filter::Digest's pod
new option 'as' => 'X' as shortcut for caller_info + caller_message
Data::Printer::Filter::PDL added to documentation