The libxml2 have previously leaked into the global namespace leading
to forced -I<include_path> for every compilation unit using isc/xml.h
header. This MR fixes the usage making the caller object opaque.
Fuzz input to dns_rdata_fromwire(). Then convert the result
to text, back to wire format, to multiline text, and back to wire
format again, checking for consistency throughout the sequence.
Add a missing semicolon to prevent "make test" run from the top-level
directory from failing even when all system and unit tests succeed due
to "(cd fuzz && ${MAKE} check)" returning a non-zero exit code.