archive classes for XML. The wide character
version (<code style="white-space: normal">xml_w?archive</code>) renders its output as UTF-8 which can
handle any wide character without loss of information. 
<code style="white-space: normal">std::string</code> data is converted from multi-byte format to wide
character format using the current <code style="white-space: normal">
locale</code>.  Hence this version should give a fair rendering of all
C++ data for all cases.  This could result in some unexpected beha