BUG: using InputPixelType to hold label count can overflow.

The member variable m_TotalLabelCount is set to the maximum
pixel value in the input images, plus one. For any unsigned pixel
type if the maximum input value equals
itk::NumericTraits<InputPixelType>::max(), then the TotalLabelCount
gets set to zero, and zero-length tables end up causing memory errors
and crashes.

Change-Id: Icabc62f7917105cdf35524ab0c68fda5895ae0a4
Merge topic 'LabelVotingSizeVarBug'

5f5c64e BUG: using InputPixelType to hold label count can overflow.