processing: mm is pointer, updated api, tests

src/knot/nameserver/process_answer.c

src/knot/nameserver/process_query.c

src/knot/server/tcp-handler.c

src/knot/server/udp-handler.c

src/libknot/processing/process.c

src/libknot/processing/process.h

src/libknot/processing/requestor.c

tests/process_answer.c

tests/process_query.c