Learned more about CMake in the last hour or so than I have in the last
few years. Now I've decided to bin out all the solution files and all
the Autoconf scaffolding, I want to extend the CMake build to properly
provide the same capabilities. Steffen's given me a terrific place to
work from, for which I am hugely, if extremely belatedly, grateful.
XMLReaderInterface template. It is only interested in string_type and
string_adaptor. All the fancy TMP to extract types and what not
is only relevant in *_wrapper classes.