Update to DCMTK-3.6.1_20150924 in superbuild

CMakeExternals/DCMTK.cmake

@@ -24,7 +24,7 @@ if(DEFINED DCMTK_DIR AND NOT EXISTS ${DCMTK_DIR})
 endif()
 
 if(NOT DEFINED DCMTK_DIR AND NOT ${CMAKE_PROJECT_NAME}_USE_SYSTEM_${proj})
-  set(revision_tag ae3b946f6e6231)
+  set(revision_tag DCMTK-3.6.1_20150924)
   if(${proj}_REVISION_TAG)
     set(revision_tag ${${proj}_REVISION_TAG})
   endif()