/usr/lib/x86_64-linux-gnu/libgdk-x11-2.0.so.0 is in libgtk2.0-0 2.24.31-2.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libgdk-x11-2.0.so.0.2400.31
/usr/lib/x86_64-linux-gnu/libgdk-x11-2.0.so.0.2400.31