ENH: Update elastix to revision 5260
ENH: Update elastix to revision 5260

This update resolves an issue where the fixed image, fixed mask and
moving mask had to be deep copied before each registration  because the
images where destroyed internally after registration to conserve
memory. The fix significantly reduces the memory footprint of reusing a
SimpleElastix object for multiple registrations.

kaspermarstal/SimpleElastix,kaspermarstal/SimpleElastix,kaspermarstal/SimpleElastix,kaspermarstal/SimpleElastix,kaspermarstal/SimpleElastix,kaspermarstal/SimpleElastix,kaspermarstal/SimpleElastix