/usr/include/ktexteditor/ is in kdelibs5-dev 4:4.8.2-0ubuntu1.
This file is owned by root:root, with mode 0o755.
..
/usr/include/ktexteditor/annotationinterface.h
/usr/include/ktexteditor/attribute.h
/usr/include/ktexteditor/codecompletioninterface.h
/usr/include/ktexteditor/codecompletionmodel.h
/usr/include/ktexteditor/codecompletionmodelcontrollerinterface.h
/usr/include/ktexteditor/commandinterface.h
/usr/include/ktexteditor/configinterface.h
/usr/include/ktexteditor/configpage.h
/usr/include/ktexteditor/containerinterface.h
/usr/include/ktexteditor/cursor.h
/usr/include/ktexteditor/cursorfeedback.h
/usr/include/ktexteditor/document.h
/usr/include/ktexteditor/editor.h
/usr/include/ktexteditor/editorchooser.h
/usr/include/ktexteditor/factory.h
/usr/include/ktexteditor/highlightinterface.h
/usr/include/ktexteditor/ktexteditor_export.h
/usr/include/ktexteditor/loadsavefiltercheckplugin.h
/usr/include/ktexteditor/markinterface.h
/usr/include/ktexteditor/modeinterface.h
/usr/include/ktexteditor/modificationinterface.h
/usr/include/ktexteditor/movingcursor.h
/usr/include/ktexteditor/movinginterface.h
/usr/include/ktexteditor/movingrange.h
/usr/include/ktexteditor/movingrangefeedback.h
/usr/include/ktexteditor/plugin.h
/usr/include/ktexteditor/range.h
/usr/include/ktexteditor/rangefeedback.h
/usr/include/ktexteditor/recoveryinterface.h
/usr/include/ktexteditor/searchinterface.h
/usr/include/ktexteditor/sessionconfiginterface.h
/usr/include/ktexteditor/smartcursor.h
/usr/include/ktexteditor/smartcursornotifier.h
/usr/include/ktexteditor/smartcursorwatcher.h
/usr/include/ktexteditor/smartinterface.h
/usr/include/ktexteditor/smartrange.h
/usr/include/ktexteditor/smartrangenotifier.h
/usr/include/ktexteditor/smartrangewatcher.h
/usr/include/ktexteditor/templateinterface.h
/usr/include/ktexteditor/templateinterface2.h
/usr/include/ktexteditor/texthintinterface.h
/usr/include/ktexteditor/variableinterface.h
/usr/include/ktexteditor/view.h