/usr/include/d/ is in libvibe-http-dev 0.8.2-1build1.
This file is owned by root:root, with mode 0o755.
..
/usr/include/d/vibe/
/usr/include/d/vibe/vibe/
/usr/include/d/vibe/vibe/http/
/usr/include/d/vibe/vibe/http/auth/
/usr/include/d/vibe/vibe/http/auth/basic_auth.d
/usr/include/d/vibe/vibe/http/auth/digest_auth.d
/usr/include/d/vibe/vibe/http/client.d
/usr/include/d/vibe/vibe/http/common.d
/usr/include/d/vibe/vibe/http/dist.d
/usr/include/d/vibe/vibe/http/fileserver.d
/usr/include/d/vibe/vibe/http/form.d
/usr/include/d/vibe/vibe/http/log.d
/usr/include/d/vibe/vibe/http/proxy.d
/usr/include/d/vibe/vibe/http/router.d
/usr/include/d/vibe/vibe/http/server.d
/usr/include/d/vibe/vibe/http/session.d
/usr/include/d/vibe/vibe/http/status.d
/usr/include/d/vibe/vibe/http/websockets.d