Juan 18/08/2018 : mode_exchange_ll.f90 , Bug on MPI_RECV <-> uninitialized IMAXSIZESEND/IMAXSIZERECV variables (not used but introduce bug in allocation with negative size)

Juan 17/07/2018 :fmread_ll.f90, PB out of memory in MPI_BSEND => reintroduce needed MPI_BARRIER in IO_READ_FIELD_BYFIELD_X3

Juan 11/07/2018:Makefile, cleancdf => add make clean to all component to better cleaning/install reproductibility

* Rules.LXifort.mk: use gcc for C compilation + add O2 OPTLEVEL
* Makefile: add FFLAGS to netCDF configure

Philippe 04/07/2018: SURFEX: bug correction: PLMO must be declared POINTER because it can be passed non associated

Philippe 28/06/2018: IO: if a file is not found in the requested fileformat, try the other one (LFI or NetCDF)

(cherry picked from commit 3580a7c0)

* R4 are now written in netCDF files as simple precision
* files can be read even if written with different integer or real precisions
* new attributes for netCDF files: MNH_REAL and MNH_INT
* several small bug corrected