- Fix CheckFor64BitStreams to not re-check every time
  - Remove status messages from Xdmf2/*/CMakeLists.txt:
     "Finding Atomic Data Sizes"
     "Finding a 64 Bit Integer"
     "Checking for 64 Bit Streams"
    These messages are confusing since they appear every time.
    The CMakeOutput.txt and CMakeError.txt log files should have
    information about these checks when they are performed the
    first time anyway.