performance

Merge pull request #9 in HDFFV/performance from ~LRKNOX/performance_lrk:master to master

* commit '002e7b470a0ed49166b58276f92e518505083522':
  Add option -l L where L will replace the default MAX_TIME_LEVEL.  This changes the size of the datasets created by h5core to allow the benchmark to run on systems not having enough memory for the original size datasets.