Fix potentially undefined behavior when filling valueint

If the number is bigger or smaller than the biggest or smallest integer,
the behavior would be undefined.

This commit defines it as saturation behavior.

cJSON.c

@@ -225,7 +225,19 @@ static const unsigned char *parse_number(cJSON *item, const unsigned char *num)
     n = sign * n * pow(10.0, (scale + subscale * signsubscale));
 
     item->valuedouble = n;
-    item->valueint = (int)n;
+    /* use saturation in case of overflow */
+    if (n >= INT_MAX)
+    {
+        item->valueint = INT_MAX;
+    }
+    else if (n <= INT_MIN)
+    {
+        item->valueint = INT_MIN;
+    }
+    else
+    {
+        item->valueint = (int)n;
+    }
     item->type = cJSON_Number;
 
     return num;
@@ -2021,7 +2033,20 @@ cJSON *cJSON_CreateNumber(double num)
     {
         item->type = cJSON_Number;
         item->valuedouble = num;
-        item->valueint = (int)num;
+
+        /* use saturation in case of overflow */
+        if (num >= INT_MAX)
+        {
+            item->valueint = INT_MAX;
+        }
+        else if (num <= INT_MIN)
+        {
+            item->valueint = INT_MIN;
+        }
+        else
+        {
+            item->valueint = (int)num;
+        }
     }
 
     return item;