/usr/include/GNUstep/XMLLib/ is in adun.app 0.81-6.
This file is owned by root:root, with mode 0o755.
..
/usr/include/GNUstep/XMLLib/ULAtomListNode.h
/usr/include/GNUstep/XMLLib/ULClassNode.h
/usr/include/GNUstep/XMLLib/ULConnectivityNode.h
/usr/include/GNUstep/XMLLib/ULInteractionNode.h
/usr/include/GNUstep/XMLLib/ULMolecularLibraryNode.h
/usr/include/GNUstep/XMLLib/ULMolecularLibraryTree.h
/usr/include/GNUstep/XMLLib/ULMoleculeClassNode.h
/usr/include/GNUstep/XMLLib/ULMoleculeNode.h
/usr/include/GNUstep/XMLLib/ULParameterNode.h
/usr/include/GNUstep/XMLLib/ULParameterTree.h
/usr/include/GNUstep/XMLLib/ULTopologyNode.h
/usr/include/GNUstep/XMLLib/XMLDocumentRoot.h
/usr/include/GNUstep/XMLLib/XMLLib.h
/usr/include/GNUstep/XMLLib/XMLNode.h