VTK_SMP_BACKEND=TBB enables implicit linking to TBB
vtkAtomic is including tbb/atomich and tbb's headers on windows do #pragma based implicit linking unless the compile option __TBB_NO_IMPLICIT_LINKAGE is enabled. This means that any library that includes a vtk header file in any of it's source files must link against TBB even though tbb.lib is not in its link line. We should avoid using tbb headers in VTK's public headers or at least guard it with the option to disable implicit linkage.
@chuck.atkins @demarle Is this worth trying to get into 7.1?