/usr/include/ is in libdc-dev 0.3.24~svn3121-1.1.
This file is owned by root:root, with mode 0o755.
..
/usr/include/dclib-0.3/
/usr/include/dclib-0.3/dclib/
/usr/include/dclib-0.3/dclib/core/
/usr/include/dclib-0.3/dclib/core/casyncdns.h
/usr/include/dclib-0.3/dclib/core/cbase32.h
/usr/include/dclib-0.3/dclib/core/cbase64.h
/usr/include/dclib-0.3/dclib/core/cbytearray.h
/usr/include/dclib-0.3/dclib/core/cbz.h
/usr/include/dclib-0.3/dclib/core/ccallback.h
/usr/include/dclib-0.3/dclib/core/cconnection.h
/usr/include/dclib-0.3/dclib/core/cdir.h
/usr/include/dclib-0.3/dclib/core/cfile.h
/usr/include/dclib-0.3/dclib/core/che3.h
/usr/include/dclib-0.3/dclib/core/ciconv.h
/usr/include/dclib-0.3/dclib/core/clisten.h
/usr/include/dclib-0.3/dclib/core/clist.h
/usr/include/dclib-0.3/dclib/core/clogfile.h
/usr/include/dclib-0.3/dclib/core/cmanager.h
/usr/include/dclib-0.3/dclib/core/cmutex.h
/usr/include/dclib-0.3/dclib/core/cnetaddr.h
/usr/include/dclib-0.3/dclib/core/cplugin.h
/usr/include/dclib-0.3/dclib/core/csingleton.h
/usr/include/dclib-0.3/dclib/core/csocket.h
/usr/include/dclib-0.3/dclib/core/cssl.h
/usr/include/dclib-0.3/dclib/core/cstring.h
/usr/include/dclib-0.3/dclib/core/cstringhash.h
/usr/include/dclib-0.3/dclib/core/cstringlist.h
/usr/include/dclib-0.3/dclib/core/cthread.h
/usr/include/dclib-0.3/dclib/core/ctraffic.h
/usr/include/dclib-0.3/dclib/core/cxml.h
/usr/include/dclib-0.3/dclib/core/czlib.h
/usr/include/dclib-0.3/dclib/core/platform.h
/usr/include/dclib-0.3/dclib/core/types.h
/usr/include/dclib-0.3/dclib/ccasefolder.h
/usr/include/dclib-0.3/dclib/cclient.h
/usr/include/dclib-0.3/dclib/cclientssl.h
/usr/include/dclib-0.3/dclib/cconfig.h
/usr/include/dclib-0.3/dclib/cconnectionmanager.h
/usr/include/dclib-0.3/dclib/cdcproto.h
/usr/include/dclib-0.3/dclib/cdownloadmanager.h
/usr/include/dclib-0.3/dclib/cdownloadqueue.h
/usr/include/dclib-0.3/dclib/cencrypt.h
/usr/include/dclib-0.3/dclib/cfilehasher.h
/usr/include/dclib-0.3/dclib/cfilemanager.h
/usr/include/dclib-0.3/dclib/chttp.h
/usr/include/dclib-0.3/dclib/chublistmanager.h
/usr/include/dclib-0.3/dclib/clistenmanager.h
/usr/include/dclib-0.3/dclib/cmessagehandler.h
/usr/include/dclib-0.3/dclib/cpluginmanager.h
/usr/include/dclib-0.3/dclib/cquerymanager.h
/usr/include/dclib-0.3/dclib/csearchindex.h
/usr/include/dclib-0.3/dclib/csearchmanager.h
/usr/include/dclib-0.3/dclib/csearchsocket.h
/usr/include/dclib-0.3/dclib/csharelist.h
/usr/include/dclib-0.3/dclib/csharetreefolder.h
/usr/include/dclib-0.3/dclib/ctransfer.h
/usr/include/dclib-0.3/dclib/cuserlist.h
/usr/include/dclib-0.3/dclib/cutils.h
/usr/include/dclib-0.3/dclib/dclib.h
/usr/include/dclib-0.3/dclib/dclib-ssl-use.h
/usr/include/dclib-0.3/dclib/dclib-stl-use.h
/usr/include/dclib-0.3/dclib/dcobject.h
/usr/include/dclib-0.3/dclib/dcos.h