Fix _nd_image.geometric_transform endianness bug

* Add _geometric_transform python wrapper to do byteswapping if 'output'
  dtype does not have a native endianness
* Add a few tests with 'ouput' parameter + native and non-native
endianness dtype
Fix for numpy.empty_like in numpy version 1.5

numpy.empty_like does not have dtype parameter
Merge pull request #4150 from lesteve/fix-ndimage-geometric-transform-non-native-endianness-bug

BUG: ndimage: fix _nd_image.geometric_transform endianness bug