darshan-merge doesn't work as general purpose tool for combining darshan logs

[shanedsnyder]

darshan-merge was originally written to help merge together per-process Darshan logs generated using Darshan's mmap logging mechanism. It does not work properly when merging together Darshan logs from multiple jobs that access some of the same files -- in that case, shared records are taken completely from just one of the input logs, rather than creating a record using aggregated data from all processes.