COMP: Missing breaks in swithc

1150783-1150785 Execution falls through to the next case statement or
default

Change-Id: I2bf7e62feba71cddf4958473ee941c6a4e1691ab
PERF: Reviewing code for facilitating compiler optimizations

The itkLinearInterpolateImageFunction.h is such a core
function, it deserves special attention for gaining
any amount of speed improvement can help
improve the speed of many programs.

Conflicts:
	Modules/Core/ImageFunction/include/itkLinearInterpolateImageFunction.h
	Modules/Core/ImageFunction/include/itkVectorLinearInterpolateImageFunction.hxx

Change-Id: Ibba6caa0468e850ab6b487565943d07af9f82f8c
COMP: fix failing voronoi segmentation tests

Internal comp method used for std::sort didn't induce a strict weak
ordering ( <= vs < ) as required, since it returned true on
equal. This cause failures likely due to difference algorithms in
libc++.

Change-Id: Ic4c8f61d53bce6858b4edcd3a93c605271b0c65b