Philippe 14/01/2021: bugfixes for aircraft_balloon_evol:

-ZXCOEF and ZYCOEF were not computed if CVBALL
-PCIT was used if CCLOUD/=ICEx (not allocated)
-PSEA was always used even if not allocated (CSURF/=EXTE)
-do not use PMAP if cartesian domain

(cherry picked from commit d82def518a9d007cb8f8a827d7b872b774f4a965)