COMP: add suppression for false constant math warning

Suppress this warning seen on Ubuntu 10:

/.../SimpleITK-build/ITK-prefix/include/ITK-4.4/itkImageRegionConstIteratorWithIndex.hxx:37:
warning: assuming signed overflow does not occur when assuming that (X
+ c) < X is always false

Change-Id: I0253a30f1a922922f518462c237c3fcf4ad3593e
Merge topic 'SupressSomeWarnings' into next

f7460c9 COMP: add suppression for false constant math warning