get rid off **WARNNING** CONFIG_CHECK: useMNC is TRUE and #undef ALLOW_MNC  (already tested with exp5)
get rid off **WARNNING** CONFIG_CHECK: useMNC is TRUE and #undef ALLOW_MNC
 (already tested with exp5)

altMITgcm/MITgcm66h,altMITgcm/MITgcm66h,altMITgcm/MITgcm66h,altMITgcm/MITgcm66h,altMITgcm/MITgcm66h,altMITgcm/MITgcm66h,altMITgcm/MITgcm66h,altMITgcm/MITgcm66h