COMP: Link vtkFiltersStatisticsGnuR module to KWSys

Source files in this module include <vtksys/...> headers so we need to
link to the KWSys libraries.  Link using PRIVATE_DEPENDS in module.cmake
to get the module dependency but not expose it to dependents because no
header files propagate the dependency.

Change-Id: I7159763bf2625e88dbaa7aa8c3cee3f02cc20c90
Merge topic 'vtkFiltersStatisticsGnuR-needs-KWSys' into master

9e969ab6 COMP: Link vtkFiltersStatisticsGnuR module to KWSys