we should probably always include logs that contain dxt data in
the example output directory so we can track that module over
releases

only tested on Edison so far, and works fine

editing to clarify this regression testing is for BG systems
@ ALCF, since the scripts assume Cobalt scheduler

* mpi-io-test case now also checks that the DXT parser can handle
  a log file with no DXT data
* a new mpi-io-test was added to run with DXT tracing enabled
  to ensure DXT and it's parser are both functioning properly

- includes regression test for fprintf and fscanf
- apparently you have to wrap __isoc99_fscanf instead of fscanf
  sometimes