COMP: rename GetJacobian() to make transform ITKv4 compliant

This patch is necessary to compile Slicer with a system ITKv4 library.

I don't think that the patch is backwards compatible to ITKv3, so please handle with care.

For more info see the ITKv4 migration guide.
http://itk.org/migrationv4/index.php?action=artikel&cat=3&id=110&artlang=en