COMP: Fix DCMTK build error using a working implementation of DCMTKConfig.cmake

For details: See https://github.com/commontk/DCMTK/commit/f461865d1759854db56e4c840991c81c77e45bb9

Revert commits r21842, r21841

git-svn-id: http://svn.slicer.org/Slicer4/trunk@21849 3bd1e089-480b-0410-8dfb-8563597acbee