Versions are updated to what the mighty Schwede lab uses in production

Compilation was broken for years when IMG has been disabled.
IMG is now always built.

You might have to adapt CMake flags when building OpenStructure to variables specified here:
https://cmake.org/cmake/help/latest/module/FindPython.html

First entry is about adding the -pthread flag to resolve linking
problems. Has been observed on the scicore cluster and reported
by Yuri (FreeBSD 12.2).

As weird as it sounds but the proper var. to set is PNG_PNG_INCLUDE_DIR instead
of PNG_INCLUDE_DIR. The latter is overwritten by FindPNG and actually obsolete
(see https://github.com/Kitware/CMake/blob/master/Modules/FindPNG.cmake).

hasn't been used/tested for years