BUG: Fix BinShrinkImageFilter 32-bit failures with rounding.

Rounding is added to the integer case. There can't rounding for
floating point output, and it is not implemented for multi-component
pixel types.

Change-Id: Id15ab9932e95767769ee7e2671cd7d3a4a5bdf88
Merge topic 'BinShrink-32bit'

c06984e BUG: Fix BinShrinkImageFilter 32-bit failures with rounding.