Darshan 2.3.1-pre2 experimental release

Darshan 2.3.1-pre2 is now available on the download page for testing and feedback.  The most significant changes since 2.3.1-pre1 are better support for recent MPICH releases, examples and documentation for the -profile hooks in MPICH, and the addition of a regression testing framework.  Our plan is to feature freeze at this point and focus on platform testing for the final 2.3.1 release.

The full changelog since 2.3.0 is as follows:

* added documentation and example configuration files for using the -profile or $MPICC_PROFILE hooks to add instrumentation to MPICH-based MPI
implementations without generating custom wrapper scripts
* Add wrappers for mkstemp(), mkostemp(), mkstemps(), and mkostemps() (reported by Tom Peterka)
* Change OPEN_TIMESTAMP field to report timestamp right before open() is invoked rather than after timestamp after open is completed. NOTE: updated log format version to 2.06 to reflect this change.
* Change start_time and end_time fields in job record to use min and max (respectively) across all ranks
* Fix bug in write volume data reported in file system table in darshan-job-summary.pl (reported by Matthieu Dorier)
* Clean up autoconf test for zlib and make zlib mandatory (reported by Kalyana Chadalavada)
* add –start-group and –end-group notation to Darshan libraries for Cray PE 2.x environment to fix link-time corner cases (Yushu Yao)
* improve y axis labels on time interval graphs in darshan-job-summary.pl (reported by Tom Peterka)
* misc. improvements to darshan-parser –perf output (reported by Shane Snyder)
– indicate which rank was slowest in unique file results
– label I/O vs. meta time more clearly
– include unique file meta time in agg_perf_by_slowest calculation
* added regression test script framework in darshan-test/regression/
– workstation-static and workstation-dynamic test environments supported
* update darshan-gen-fortran.pl and darshan-gen-cxx.pl to support new library naming conventions in MPICH 3.1.1 and higher
* update documentation to reflect known issues with some versions of MPICH