Distributed MultiThreaded Checkpointing Files

Several important changes and enhancements were added:

* `dmtcp_launch/restart/command/coordinator` now take the flags
  `-h, -p, --coord-host/port` and environment variables
  `DMTCP_COORD_HOST/PORT`.  The older `--host, --port, DMTCP_HOST/PORT`
  are now deprecated.
* Newer versions of MATLAB (matlab-2013 and later) were using additional
  Linux features.  All recent versions of matlab are again supported.
* Intensive testing done for integration of MPI/SLURM
  for the following MPI dialects:  Intel MPI/MVAPICH-2/MPICH-2/Open MPI.
  See `plugin/batch-queue/job_examples/` for SLURM/DMTCP submission scripts.
  Preliminary support for some other resource managers also provided,
  especially including ibrun.
    * Open MPI version 1.8 _with_ InfiniBand is not yet supported.
      This is due to the OMPI use of UD (unreliable datagrams) for InfiniBand.
      Support is planned for the near future.  Earlier OMPI versions continue
      to work with IB.  We do not currently know of a config in OMPI-1.8 to
      avoid IB/UD (to use only IB/CM).  Such a workaround would let DMTCP work.
* Added support for newest Linux kernels: split of [vdso]
  into [vdso] and [vvar]; To see if this affects you, do:
  ```
  cat /proc/self/maps | grep '\[vvar]'
  ```
* Support for glibc version 2.21 added.  To see if this affects you, do:
  ```
  ls -l /lib*/libc.so.6 /lib/*/libc.so.6`
  ```
* The environment variable `DMTCP_GDB_ATTACH_ON_RESTART` was added.  Setting
  this permanently is a security risk. But on a temporary basis,
  it can enable easier debugging of restarted processes:
  ```
  DMTCP_GDB_ATTACH_ON_RESTART=1 dmtcp_restart ckpt_a.out_*.dmtcp &
  gdb a.out `pgrep -n a.out`
  ```
* Enhancements added for newer 32-bit ARM (armv7) CPUs
* Experimental support is now provided for 64-bit ARM (armv8)
* Bug fixes