DMTCP-2.5.1 released

This release mostly provides added robustness. Two notable items of
added functionality are:
i. DMTCP_RESTART_PAUSE and DMTCP_RESTART_PAUSE0 environment variables
for easier debugging upon initial restart
ii. The --debug-logs flag was added to dmtcp_launch/dmtcp_restart.
One can now turn on logging individually for separate plugins,
instead of only turning it on globally.

An incompatibility of DMTCP with Open MPI 1.10 when using orterun (mpirun)
was discovered. This may also affect some other versions of Open MPI 1.10.
This bug will be fixed in a future release.

• Fixed an issue when starting multiple DMTCP coordinators on same host
  at approximately the same time
• Fixed issue with PBS scheduler for HPC
• Fixed issue when restarting on a different host with a larger
  limit on the number of open file descriptors
• dmtcp_launch/dmtcp_restart now accept '--debug-logs' flag to specify
  which DMTCP plugins should produce logging information
  (It used to be all or nothing.)
• Improved robustness for IB (InfiniBand) plugin
• Fixed DMTCP_RESTART_PAUSE and DMTCP_RESTART_PAUSE0 environment variables
  for debugging upon restart
• The brk() call was failing on restart on Debian due to overly strict assert
• dmtcp_launch was hanging on some RHEL5 and RHEL6 due to deadlock with
  libc low-level locks. Fixed now.
• Updated tls_pid_offset in DMTCP to handle newer GLIBc (versions > 2.24)
• Fixed launch of 32-bit binary when forking/execing from a 64-bit executable
• Fixed issue that can affect a parent holding a malloc-lock while forking
• Fixed issue when a user thread calls 'dmtcp_get_coord_ckpt_dir()'