Philippe 30/11/2022: WATER_SUM is now a PURE function

src/MNH/water_sum.f90

-!MNH_LIC Copyright 1994-2014 CNRS, Meteo-France and Universite Paul Sabatier
+!MNH_LIC Copyright 1998-2022 CNRS, Meteo-France and Universite Paul Sabatier
 !MNH_LIC This is part of the Meso-NH software governed by the CeCILL-C licence
-!MNH_LIC version 1. See LICENSE, CeCILL-C_V1-en.txt and CeCILL-C_V1-fr.txt  
+!MNH_LIC version 1. See LICENSE, CeCILL-C_V1-en.txt and CeCILL-C_V1-fr.txt
 !MNH_LIC for details. version 1.
 !-----------------------------------------------------------------
-!--------------- special set of characters for RCS information
-!-----------------------------------------------------------------
-! $Source$ $Revision$
-! MASDEV4_7 prep_real 2006/05/18 13:07:25
-!-----------------------------------------------------------------
 !     #####################
       MODULE MODI_WATER_SUM
 !     #####################
 INTERFACE
-      FUNCTION WATER_SUM(PR) RESULT (PSUM_R)
+      PURE FUNCTION WATER_SUM(PR) RESULT (PSUM_R)
 !
 REAL,DIMENSION(:,:,:,:),              INTENT(IN) :: PR     ! water species
 REAL,DIMENSION(SIZE(PR,1),SIZE(PR,2),SIZE(PR,3)) :: PSUM_R ! sum of water species
@@ -20,9 +15,9 @@ REAL,DIMENSION(SIZE(PR,1),SIZE(PR,2),SIZE(PR,3)) :: PSUM_R ! sum of water specie
 END FUNCTION WATER_SUM
 END INTERFACE
 END MODULE MODI_WATER_SUM
-!     ######################################
-      FUNCTION WATER_SUM(PR) RESULT (PSUM_R)
-!     ######################################
+!     ###########################################
+      PURE FUNCTION WATER_SUM(PR) RESULT (PSUM_R)
+!     ###########################################
 !
 !!****  *WATER_SUM* - summation on the water species (fourth array index)
 !!