Philippe 16/11/2021: ZSOLVER: port to 5.5.0 version + correct ifdef to run without OpenACC and/or MNH_BITREP

Juan 16/11/2021:ZSOLVER, add routine zt1d_discretisation_allocate3d , for fast GPU memory allocation in MutiGrid

Juan 16/11/2021:ZSOLVER/gdiv.f90 , manage compilation with(out) MNH_OPENACC && Bug correction Z3 not allocated

Juan 16/11/2021: mode_openacc_set_device.f90,tools.f90, add _FAKEOPENACC for compile in OPENACCDEFONLY with gfortran/ifort etc ...

Juan 16/11/2021: ZSOLVER/ new source from MNH only to change intent(IN) -> INOUT for PDZX/Y , for get_halo2_d

Juan 16/11/2021: add orig source from MNH , to change intent(IN) -> INOUT for PDZX/Y , for get_halo2_d

Philippe 03/11/2021: Sources_neg_correct: always allocate zls (necessary to prevent crash with mppdb_check of it)

(modif was erroneously commited from development code)

Philippe 26/10/2021: OpenACC: create GT1DFLAT buffer that can be used for any size and shape arrays (logical)

Juan 21/10/2021:ZSOLVER/mode_exchange2_ll.f90 , For GPU=OPENACC , add orig for no managed memory init_halo2 allocation/adaptation

Juan 15/10/2021:tensor,prepare for nomanaged compilation -> replace %{dimx/y/z} in loop to avoid copyin of derived type structure

Juan 15/10/2021:tensor,prepare for nomanaged compilation ->  add enter/exit data , for allocate variables

Philippe 12/10/2021: OpenACC: Sources_neg_correct: replace where by do concurrent (workaround for nvhpc bug)