COMP: Cleanup CMP0022 and CMP0023 warnings

CMake 2.8.12 introduces policies CMP0022 and CMP0023 that trigger
warnings in some of VTK's CMake code.  Fix them as follows.  The result
is a cleaner and more explicit link specification anyway.

CMP0022 warns when we set the LINK_INTERFACE_LIBRARIES property directly
without also setting the newly introduced INTERFACE_LINK_LIBRARIES
property directly.  Simply drop these settings because they are achieved
already by use of the keyword-based target_link_libraries signature.

CMP0023 warns when we use both the plain and keyword signatures of the
target_link_libraries command for a single target.  The module macros
use the keyword signature (LINK_PUBLIC/LINK_PRIVATE), so any direct
calls to the plain target_link_libraries signature are doing "private"
linking.  Add the LINK_PRIVATE keyword to such calls to make this
explicit and avoid the warning.

Change-Id: I1e5bf687733e3f19462da698c0d5e3899439bf02