Works well 👍

-- at: /opt/intel/compilers_and_libraries_2018.0.128/linux/ipp
-- Cannot find Intel IPP IW. Checking "Intel IPP for OpenCV" package
-- IPPICV: Download: ippicv_2017u3_lnx_intel64_general_20170822.tgz
-- found Intel IPP IW sources: 2017.0.3
-- at: /home/alalek/projects/opencv/build/ipp_standalone/3rdparty/ippicv/ippicv_lnx/../ippiw_lnx/

@alalek @lupustr3
It looks like this PR will break further more IPP IW 2018 configuration for Windows platform (see #9622).
Is it possible to plan ahead for v2018 that does use iw/iw_version.h instead of iw/iw_ll.h ?

@fmigneault This fix workarounds problem with Cannot open include file: 'iw/iw_ll.h': No such file or directory.
Currently OpenCV rely on low-level functions from IPP IW which is not a part of public API, so "standalone" IPP IW can't be used directly for now.