BUG: Fix black image from vtkImageReslice in slab mode.

Platforms that used gcc-4.7 were producing black images on
TestImageResliceMapperSlab and other tests that used vtkImageReslice
in its "slab" mode.  I built gcc-4.7 on my own machine and was
able to reproduce the bug.  A pointer to an array was being used
after the end of the scope in which the array had been declared

Change-Id: I76340f8a5d029067b879e5d2c1c3d9229591e54e
Merge topic 'reslice-slab-black' into master

8ba58dcf BUG: Fix black image from vtkImageReslice in slab mode.