Add a typecast to avoid 32-bit integer overflow in the concat_ws()

function with an enormous separator values and many arguments.

FossilOrigin-Name: 498e3f1cf57f164fbd8380e92bf91b9f26d6aa05d092fcd135d754abf1e5b1b5

src/func.c

@@ -1570,7 +1570,7 @@ static void concatFuncCore(
   for(i=0; i<argc; i++){
     n += sqlite3_value_bytes(argv[i]);
   }
-  n += (argc-1)*nSep;
+  n += (argc-1)*(i64)nSep;
   z = sqlite3_malloc64(n+1);
   if( z==0 ){
     sqlite3_result_error_nomem(context);