SL-821: Add WSTRINGIZE() and DEWSTRINGIZE() macros for wide strings.

Streamline convenience overload stringize(std::wstring); make convenience
overload wstringize(std::string) symmetrically convert from UTF-8 string.

Also eliminate STRINGIZE() et al. dependency on Boost.Phoenix: use lambdas
instead.

Using lambdas instead of template expansion necessitates reordering some code
in wrapllerrs.h.