Mark BROKEN: fails to build

In file included from application.cpp:16:
In file included from ./comparison.h:11:
In file included from ./lib/process_xml.h:10:
In file included from ../../zen/xml_io.h:10:
In file included from /usr/local/include/zenxml/xml.h:10:
In file included from /usr/local/include/zenxml/bind.h:12:
/usr/local/include/zenxml/parser.h:99:40: error: use of undeclared identifier 'hexify'

const auto hexDigits = hexify(c);
                       ^

/usr/local/include/zenxml/parser.h:170:27: error: use of undeclared identifier 'unhexify'

output += unhexify(it[3], it[4]);
          ^

Reported by: pkg-fallout