DMTCP 2.2 released

DMTCP version 2.2. has now been released.

In this release, the lowest layers have been re-organized and partially
re-written for greater clarity of code and greater maintainability.
These changes should be transparent to end users.

Users relying on the use of DMTCP with MPI, InfiniBand or the Toruqe or
SLURM batch queues are strongly advised to upgrade.

Other changes are:

• A --exit-after-ckpt flag was added for dmtcp_coordinator.
• Scalability improvements were added. DMTCP has now been tested
  on an MPI jobs using 2048 MPI ranks over 2048 CPU cores.
• Anybody using DMTCP with InfiniBand is strongly recommended to upgrade
  to inherit important bug fixes. The InfiniBand plugin is still
  formally part of the 'contrib' directory during this release. It was
  tested primarily against Open MPI. Further testing is still needed
  before the InfiniBand plugin can be promoted from the 'contrib'
  directory to the 'plugin' directory.
• The --infiniband flag of dmtcp_launch was not fully functional in
  version 2.1. This is now fixed.
• The 'dmtcp_launch --no-coordinator' option was broken in version 2.1.
  This is now fixed.
• The --disable-dl-plugin flag was added to dmtcp_launch. Most users will
  not need this option. But software relying on DT_RPATH, DT_RUNPATH,
  or certain other uncommon cases in loading dynamic libraries may need
  to invoke this for stability. It is hoped to remove the need for this
  flag in a future release.
• A similar comment holds for the --disable-alloc-plugin flag in dmtcp_launch.
  If there appear to be issues with a memory allocator, consider invoking
  this flag.
• Numerous minor bug fixes and enhancements were added.