use Exporter::Tiny instead of Pragmatic

--HG--
branch : XML-LibXML-PrettyPrint
backport to Perl 5.8.1

--HG--
branch : XML-LibXML-PrettyPrint
modernize test suite; use Test::Warnings instead of Test::Warn; rely on newer Test::More

--HG--
branch : XML-LibXML-PrettyPrint