- Rename compat-openmpiXY to openmpi-X.Y. Package names, directories,
  modulefiles.
- Ship multiple openmpi versions:
  - openmpi-1.4   (compat with RHEL 6.0, 6.1)
  - openmpi-1.5.3 (compat with RHEL 6.2)
  - openmpi-1.5.4 (compat with RHEL 6.3, 6.4, 6.5)
  - openmpi-1.8   (compat with RHEL 6.6, 6.7)
- Avoid breakage in transition from the compat-openmpi package from RHEL 6.7
  (was versioned as 1.4.3, but was in fact a chimera of 1.4.3 and 1.5.3,
   where really only 1.5.3 had any chance of working) by keeping the
  "compat-openmpi", "compat-openmpi-$arch" directory and module names
  for openmpi-1.5.3.
- openmpi-1.8 keeps the module and directory unversioned names "openmpi",
  "openmpi-$arch" it had in RHEL 6.7.
- Related: rhbz1158864