Changeset 1520 for LMDZ5/trunk/libf/dyn3dpar/exner_milieu.F

Implementation of a different vertical discretization (from/for planets, but
can in principle also be used for Earth).
Choice of vertical discretization is set by flag 'disvert_type';
'disvert_type=1' is Earth standard (default; ie set to 1 if
planet_type=="earth") case.
With 'disvert_type=2', approximate altitude of layers and reference atmospheric
scale height must be given using an input file ("z2sig.def", first line
should give scale height, in km, following lines must specify the altitude,
in km above surface, of mid-layers, one per line; see disvert_noterre.F).

Checked that these changes do not impact on 'bench' results, on Vargas.

EM.