Update dcmtk to rev 19 via SR 749834
    
    https://build.opensuse.org/request/show/749834
    by user dimstar_suse
    - Update to 3.6.5. See DOCS/CHANGES.365 for more information
      * Updated code definitions for DICOM 2018e
      * Fix some -Wunused-result warnings warnings
      * Fixed CMake error if "FindPkgConfig" is missing