be safe at headers file name

src/include/66/backup.h

src/include/66/constants.h

src/include/66/db.h

src/include/66/enum.h

src/include/66/hpr.h

src/include/66/rc.h

src/include/66/resolve.h

src/include/66/ssexec.h

src/include/66/state.h

src/include/66/svc.h

src/include/66/tree.h

src/include/66/utils.h