Revision 190

Created module cv_thermo_m around procedure cv_thermo. Moved variables
from module cvthermo to module cv_thermo_m, where they are defined.

In ini_histins and initphysto, using part of rlon and rlat from
phyetat0_m is pretending that we do not know about the dynamical grid,
while the way we extract zx_lon(:, 1) and zx_lat(1, :) depends on
ordering inside rlon and rlat. So we might as well simplify and
clarify by using directly rlonv and rlatu.

Removed intermediary variables in write_histins and phystokenc.