/usr/share/man/man3/XineramaIsActive.3.gz is in libxinerama-dev 2:1.1.1-3build1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/man/man3/Xinerama.3.gz
/usr/share/man/man3/Xinerama.3.gz