- fix so that it compiles without MPI; fix syntax in setting [n,s,e,w,]Side logicals - rename S/R EXCH2_RL_SEND_PUT_VEC -> EXCH2_SEND_PUT_VEC_RL      and S/R EXCH2_RL_RECV_GET_VEC -> EXCH2_RECV_GET_VEC_RL   so that it closer to file names (exch_send_put_vec.F, exch_recv_get_vec.F)   and match the printed messages - move calls to MPI_Wait from FLT_EXCH2 to EXCH2_RECV_GET_VEC_RL   (so that flt_exch2.F is free from MPI stuff) - move BARRIER calls directly in flt_exch2.F (easier to follow) - fix multi-threaded MPI (had many issues)
- fix so that it compiles without MPI; fix syntax in setting [n,s,e,w,]Side logicals
- rename S/R EXCH2_RL_SEND_PUT_VEC -> EXCH2_SEND_PUT_VEC_RL
     and S/R EXCH2_RL_RECV_GET_VEC -> EXCH2_RECV_GET_VEC_RL
  so that it closer to file names (exch_send_put_vec.F, exch_recv_get_vec.F)
  and match the printed messages
- move calls to MPI_Wait from FLT_EXCH2 to EXCH2_RECV_GET_VEC_RL
  (so that flt_exch2.F is free from MPI stuff)
- move BARRIER calls directly in flt_exch2.F (easier to follow)
- fix multi-threaded MPI (had many issues)

altMITgcm/MITgcm66h,altMITgcm/MITgcm66h,altMITgcm/MITgcm66h,altMITgcm/MITgcm66h,altMITgcm/MITgcm66h,altMITgcm/MITgcm66h,altMITgcm/MITgcm66h,altMITgcm/MITgcm66h