/usr/include/kdevplatform/interfaces/ is in kdevelop-dev 4:5.2.1-1ubuntu4.
This file is owned by root:root, with mode 0o755.
..
/usr/include/kdevplatform/interfaces/configpage.h
/usr/include/kdevplatform/interfaces/context.h
/usr/include/kdevplatform/interfaces/contextmenuextension.h
/usr/include/kdevplatform/interfaces/iassistant.h
/usr/include/kdevplatform/interfaces/ibuddydocumentfinder.h
/usr/include/kdevplatform/interfaces/icompletionsettings.h
/usr/include/kdevplatform/interfaces/icore.h
/usr/include/kdevplatform/interfaces/idebugcontroller.h
/usr/include/kdevplatform/interfaces/idocument.h
/usr/include/kdevplatform/interfaces/idocumentation.h
/usr/include/kdevplatform/interfaces/idocumentationcontroller.h
/usr/include/kdevplatform/interfaces/idocumentationprovider.h
/usr/include/kdevplatform/interfaces/idocumentationproviderprovider.h
/usr/include/kdevplatform/interfaces/idocumentcontroller.h
/usr/include/kdevplatform/interfaces/ilanguagecheck.h
/usr/include/kdevplatform/interfaces/ilanguagecheckprovider.h
/usr/include/kdevplatform/interfaces/ilanguagecontroller.h
/usr/include/kdevplatform/interfaces/ilaunchconfiguration.h
/usr/include/kdevplatform/interfaces/ilauncher.h
/usr/include/kdevplatform/interfaces/ilaunchmode.h
/usr/include/kdevplatform/interfaces/interfacesexport.h
/usr/include/kdevplatform/interfaces/ipartcontroller.h
/usr/include/kdevplatform/interfaces/iplugin.h
/usr/include/kdevplatform/interfaces/iplugincontroller.h
/usr/include/kdevplatform/interfaces/ipluginversion.h
/usr/include/kdevplatform/interfaces/iproblem.h
/usr/include/kdevplatform/interfaces/iproject.h
/usr/include/kdevplatform/interfaces/iprojectcontroller.h
/usr/include/kdevplatform/interfaces/iprojectprovider.h
/usr/include/kdevplatform/interfaces/iruncontroller.h
/usr/include/kdevplatform/interfaces/iruntime.h
/usr/include/kdevplatform/interfaces/iruntimecontroller.h
/usr/include/kdevplatform/interfaces/iselectioncontroller.h
/usr/include/kdevplatform/interfaces/isession.h
/usr/include/kdevplatform/interfaces/isessionlock.h
/usr/include/kdevplatform/interfaces/isourceformatter.h
/usr/include/kdevplatform/interfaces/isourceformattercontroller.h
/usr/include/kdevplatform/interfaces/istatus.h
/usr/include/kdevplatform/interfaces/itemplateprovider.h
/usr/include/kdevplatform/interfaces/itestcontroller.h
/usr/include/kdevplatform/interfaces/itestsuite.h
/usr/include/kdevplatform/interfaces/itoolviewactionlistener.h
/usr/include/kdevplatform/interfaces/iuicontroller.h
/usr/include/kdevplatform/interfaces/launchconfigurationpage.h
/usr/include/kdevplatform/interfaces/launchconfigurationtype.h