XML::Handler::Trees provides three PerlSAX handler classes for
building tree structures. XML::Handler::Tree builds the same type
of tree as the "Tree" style in XML::Parser. XML::Handler::EasyTree
builds the same type of tree as the "EasyTree" style added to
XML::Parser by XML::Parser::EasyTree. XML::Handler::TreeBuilder
builds the same type of tree as Sean M. Burke's XML::TreeBuilder.
These classes make it possible to construct these tree structures
from sources other than XML::Parser.
