GNU R XML parser

 This GNU R package works with XML files using a simple, consistent
 interface. Built on top of the 'libxml2' C library.
 .
 Modifying existing XML can be done in xml2 by using the replacement functions
 of the accessors. They all have methods for both individual `xml_node` objects
 as well as `xml_nodeset` objects. If a vector of values is provided it is
 applied piecewise over the nodeset, otherwise the value is recycled.