Update to OpenMPI 1.6.4

Here is a list of changes in v1.6.4 as compared to v1.6.3:

- Fix Cygwin shared memory and debugger plugin support.  Thanks to
  Marco Atzeri for reporting the issue and providing initial patches.
- Fix to obtaining the correct available nodes when a rankfile is
  providing the allocation.  Thanks to Siegmar Gross for reporting the
  problem.
- Fix process binding issue on Solaris.  Thanks to Siegmar Gross for
  reporting the problem.
- Updates for MXM 2.0.
- Major VT update to 5.14.2.3.
- Fixed F77 constants for Cygwin/Cmake build.
- Fix a linker error when configuring --without-hwloc.
- Automatically provide compiler flags that compile properly on some
  types of ARM systems.
- Fix slot_list behavior when multiple sockets are specified.  Thanks
  to Siegmar Gross for reporting the problem.
- Fixed memory leak in one-sided operations.  Thanks to Victor
  Vysotskiy for letting us know about this one.
- Added performance improvements to the OpenIB (OpenFabrics) BTL.
- Improved error message when process affinity fails.
- Fixed MPI_MINLOC on man pages for MPI_REDUCE(_LOCAL).  Thanks to Jed
  Brown for noticing the problem and supplying a fix.
- Made malloc hooks more friendly to IO interprosers.  Thanks to the
  bug report and suggested fix from Darshan maintainer Phil Carns.
- Restored ability to direct launch under SLURM without PMI support.
- Fixed MPI datatype issues on OpenBSD.
- Major VT update to 5.14.2.3.
- Support FCA v3.0+.
- Fixed header file problems on OpenBSD.
- Fixed issue with MPI_TYPE_CREATE_F90_REAL.
- Fix an issue with using external libltdl installations.  Thanks to
  opolawski for identifying the problem.
- Fixed MPI_IN_PLACE case for MPI_ALLGATHER for FCA.
- Allow SLURM PMI support to look in lib64 directories.  Thanks to
  Guillaume Papaure for the patch.
- Restore "use mpi" ABI compatibility with the rest of the 1.5/1.6
  series (except for v1.6.3, where it was accidentally broken).
- Fix a very old error in opal_path_access(). Thanks to Marco Atzeri
  for chasing it down.

(asau)