Philippe 22/06/2022: gamma functions are now declared PURE

src/MNH/gamma.f90

-!MNH_LIC Copyright 1995-2019 CNRS, Meteo-France and Universite Paul Sabatier
+!MNH_LIC Copyright 1995-2022 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 for details. version 1.
@@ -9,13 +9,13 @@
 !
 INTERFACE GAMMA
 !
-FUNCTION GAMMA_X0D(PX)  RESULT(PGAMMA)
+PURE FUNCTION GAMMA_X0D(PX)  RESULT(PGAMMA)
 !$acc routine seq
 REAL, INTENT(IN)                                  :: PX
 REAL                                              :: PGAMMA
 END FUNCTION GAMMA_X0D
 !
-FUNCTION GAMMA_X1D(PX)  RESULT(PGAMMA)
+PURE FUNCTION GAMMA_X1D(PX)  RESULT(PGAMMA)
 REAL, DIMENSION(:), INTENT(IN)                    :: PX
 REAL, DIMENSION(SIZE(PX))                         :: PGAMMA
 END FUNCTION GAMMA_X1D
@@ -30,9 +30,9 @@ END MODULE MODI_GAMMA
 !*       1.   FUNCTION GAMMA FOR SCALAR VARIABLE
 ! 
 !
-!     ######################################
-      FUNCTION GAMMA_X0D(PX)  RESULT(PGAMMA)
-!     ######################################
+!     ###########################################
+      PURE FUNCTION GAMMA_X0D(PX)  RESULT(PGAMMA)
+!     ###########################################
 !
 !
 !!****  *GAMMA * -  Gamma  function
@@ -67,6 +67,7 @@ END MODULE MODI_GAMMA
 !!    -------------
 !!      Original     7/11/95
 !!      C. Barthe    9/11/09  add a function for 1D arguments
+!  P. Wautelet 22/06/2022: GAMMA_X0D is now declared PURE
 !
 !*       0. DECLARATIONS
 !           ------------
@@ -153,9 +154,9 @@ END FUNCTION GAMMA_X0D
 !*       1.   FUNCTION GAMMA FOR 1D ARRAY
 ! 
 !
-!     ######################################
-      FUNCTION GAMMA_X1D(PX)  RESULT(PGAMMA)
-!     ######################################
+!     ###########################################
+      PURE FUNCTION GAMMA_X1D(PX)  RESULT(PGAMMA)
+!     ###########################################
 !
 !
 !!****  *GAMMA * -  Gamma  function
@@ -189,6 +190,7 @@ END FUNCTION GAMMA_X0D
 !!    MODIFICATIONS
 !!    -------------
 !!      Original     7/11/95
+!  P. Wautelet 22/06/2022: GAMMA_X1D is now declared PURE
 !!
 !-------------------------------------------------------------------------------
 !