/usr/include/heimntlm-protos.h is in heimdal-dev 1.6~git20131207+dfsg-1ubuntu1.2.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/include/heimdal/heimntlm-protos.h
/usr/include/heimdal/heimntlm-protos.h