HCOLL:  Fix OMPI to HCOLL predefined datatypes, Ops mapping
OMPI: btl openib: fix max registarable memory caluclation

    - by default allow to register maximum possible (i.e 2 * total_memory)
      memory. This beheviour can be turned off using mca parameter
      "btl_openib_allow_max_memory_registration"

    - In fallback case, use device specific parameters to calulate
      memory limit.