Detect C++11 nullptr keyword define SITK_NULLPTR as it or NULL

There is a compatibility issue with std::tr1::function and c++11
std::function. The former accepts the C NULL defined, while the later
does not and requires the new nullptr of nullptr_t type. So the
SITK_NULLPTR is introduced to take are of this issue.

Change-Id: I71f33a5dcfd1372fee55ffa9f8a4a4ca02c3f8a1
Adding testing for affine transformation

Change-Id: I5ef34b765679b88385ab9ab30e7411fc71039f6e
Merge topic 'SIMPLEITK-555_RefactorTransformWithSpecifcObjects' into next

c2cd630a Adding testing for affine transformation
b81e514c Detect C++11 nullptr keyword define SITK_NULLPTR as it or NULL