Add missing argument for error code to MPI calls

Almost all MPI functions in Fortran need an additional argument for
returning an error code. If there is no memory allocated that receives
that error code, unrelated memory on the stack(?) could be overwritten.
(What part of the memory is overwritten might depend on the calling
convention.)

Add that argument when calling MPI subroutines in `ParallelUtils.F90`.

fem/src/ParallelUtils.F90

@@ -1386,21 +1386,21 @@ END SUBROUTINE ParallelActiveBarrier
 
 
     FUNCTION ParallelSlicesComm() RESULT( CustomComm )
-      INTEGER :: CustomComm      
-#ifdef PARALLEL_FOR_REAL      
+      INTEGER :: CustomComm
+#ifdef PARALLEL_FOR_REAL
       LOGICAL :: Visited = .FALSE.
-      INTEGER :: nSlices, nTimes, iSlice, iTime
+      INTEGER :: nSlices, nTimes, iSlice, iTime, ierr
       INTEGER :: CustomComm0
       LOGICAL :: GotIt
       SAVE Visited, CustomComm0
-      
+
       IF(.NOT. Visited ) THEN
         nSlices = ListGetInteger( CurrentModel % Simulation,'Number Of Slices',GotIt)
         nTimes = ListGetInteger( CurrentModel % Simulation,'Number Of Times',GotIt)
         IF(nSlices > 1 .AND. nTimes > 1) THEN
-          iSlice = MODULO( ParEnv % MyPe, nSlices )           
+          iSlice = MODULO( ParEnv % MyPe, nSlices )
           iTime = ParEnv % MyPe / nSlices 
-          CALL MPI_Comm_split(ELMER_COMM_WORLD, iTime, ParEnv % PEs, CustomComm0);
+          CALL MPI_Comm_split(ELMER_COMM_WORLD, iTime, ParEnv % PEs, CustomComm0, ierr);
         ELSE
           CustomComm0 = ELMER_COMM_WORLD
         END IF
@@ -1415,57 +1415,57 @@ FUNCTION ParallelSlicesComm() RESULT( CustomComm )
 
     END FUNCTION ParallelSlicesComm
 
-    
+
     FUNCTION ParallelTimesComm() RESULT( CustomComm )
-      INTEGER :: CustomComm      
-#ifdef PARALLEL_FOR_REAL      
+      INTEGER :: CustomComm
+#ifdef PARALLEL_FOR_REAL
       LOGICAL :: Visited = .FALSE.
-      INTEGER :: nSlices, nTimes, iSlice, iTime
+      INTEGER :: nSlices, nTimes, iSlice, iTime, ierr
       INTEGER :: CustomComm0
       LOGICAL :: GotIt
       SAVE Visited, CustomComm0
-      
+
       IF(.NOT. Visited ) THEN
         nSlices = ListGetInteger( CurrentModel % Simulation,'Number Of Slices',GotIt)
         nTimes = ListGetInteger( CurrentModel % Simulation,'Number Of Times',GotIt)
         IF(nSlices > 1 .AND. nTimes > 1) THEN
-          iSlice = MODULO( ParEnv % MyPe, nSlices )           
-          iTime = ParEnv % MyPe / nSlices 
-          CALL MPI_Comm_split(ELMER_COMM_WORLD, iSlice, ParEnv % PEs, CustomComm0);
+          iSlice = MODULO( ParEnv % MyPe, nSlices )
+          iTime = ParEnv % MyPe / nSlices
+          CALL MPI_Comm_split(ELMER_COMM_WORLD, iSlice, ParEnv % PEs, CustomComm0, ierr);
         ELSE
           CustomComm0 = ELMER_COMM_WORLD
         END IF
         PRINT *,'Creating TimesComm:',ParEnv % MyPe, iSlice, iTime
         Visited = .TRUE.
       END IF
-      
+
       CustomComm = CustomComm0
 #else
       CustomComm = -1
-#endif      
+#endif
     END FUNCTION ParallelTimesComm
 
 
     FUNCTION ParallelPieceRank(CustomComm) RESULT (CommRank)
-      INTEGER :: CustomComm, CommRank
+      INTEGER :: CustomComm, CommRank, ierr
 #ifdef PARALLEL_FOR_REAL
       PRINT *,'GetRank:',ParEnv % MyPe, CustomComm
-      CALL MPI_Comm_rank(CustomComm, CommRank)
+      CALL MPI_Comm_rank(CustomComm, CommRank, ierr)
       PRINT *,'GotRank:',ParEnv % MyPe, CommRank
 #else
       CommRank = -1 
-#endif       
+#endif
     END FUNCTION ParallelPieceRank
 
     FUNCTION ParallelPieceSize(CustomComm) RESULT (CommSize)
-      INTEGER :: CustomComm, CommSize
+      INTEGER :: CustomComm, CommSize, ierr
 #ifdef PARALLEL_FOR_REAL
       PRINT *,'GetSize:',ParEnv % MyPe, CustomComm
-      CALL MPI_Comm_size(CustomComm, CommSize)
+      CALL MPI_Comm_size(CustomComm, CommSize, ierr)
       PRINT *,'GotSize:',ParEnv % MyPe, CommSize
 #else
       CommRank = -1 
-#endif       
+#endif
     END FUNCTION ParallelPieceSize