[修改] 增加freeRTOS

1. 版本FreeRTOSv202212.01，命名为kernel；

kernel/FreeRTOS-Plus/Source/FreeRTOS-Cellular-Interface/test/cbmc/stubs/snprintf.c

@@ -0,0 +1,42 @@
+/*
+ * FreeRTOS-Cellular-Interface v1.3.0
+ * Copyright (C) 2021 Amazon.com, Inc. or its affiliates.  All Rights Reserved.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to
+ * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
+ * the Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
+ * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ *
+ * https://www.FreeRTOS.org
+ * https://github.com/FreeRTOS
+ */
+
+/**
+ * @file snprintf.c
+ * @brief Creates a stub for snprintf. This stub checks if, for the input copy
+ * length, the destination and source are valid accessible memory.
+ */
+
+#include <stdio.h>
+
+int snprintf( char * s,
+              size_t n,
+              const char * format,
+              ... )
+{
+    __CPROVER_assert( __CPROVER_w_ok( s, n ), "write" );
+    __CPROVER_assert( __CPROVER_r_ok( s, n ), "read" );
+    return n;
+}