Several updates to surface forcing adjustment and exit_flag

[arango]

We continue improving the 4DVAR adjustment of surface forcing fields. It is now working for several outer loops. Many thanks to Gregoire Broquet for continuing testing of this tricky algorithm. We are very happy that this it is working nicely now. We will examine the Lanczos part next.

I also continue in my cleaning of the exit_flag for all the drivers. This is part of the slow transition to parallel IO.

We are working on the preconditioning algorithm now. Upgrades and fixes to the Lanczos algorithm are on the works.

I also corrected a parallel bug in mod_netcdf.F when broadcasting var_Achar. I am now forcing initialization of all generic module variables every time that netcdf_get_dim and netcdf_inq_var is called.