Branch 2017/dev_r8126_ROBUST08_no_ghost. Add generic routine for the north fold operation without global width arrays or MPI_ALLGATHER operations (lbc_nfd_nogather_generic.h90). Actually the generic form is not strictly neccessary since only the 4d array version is used. Other possibilities are currently commented out. This commit includes fixes to mpp_nfd_generic.h90 which ensure only necessary arrays are allocated depending on ln_nnogather setting. Tested with ORCA2LIMPIS_LONG SETTE test and produces identical results with ln_nnogather true or false.