oshmem mmap: new mca parameters were introduced - sshmem_mmap_anonymous,...

... sshmem_mmap_fixed and sshmem_base_backing_file_dir - for runtime mmap management.

(ompi commits: open-mpi/ompi@ce4ee2aa8d960eb72292f5bb64108e5a85796e1d, open-mpi/ompi@3e7002e8aad2a2fe0835c67b9714dceef3c4b31b, open-mpi/ompi@b2a93943dc5cc7602cb8ed83e65524452beb82c7)