[修改] 增加freeRTOS

1. 版本FreeRTOSv202212.01，命名为kernel；

kernel/FreeRTOS-Plus/Source/FreeRTOS-Plus-TCP/test/cbmc/stubs/cbmc.c

@@ -0,0 +1,12 @@
+#include "cbmc.h"
+
+/****************************************************************
+* Model a malloc that can fail (CBMC malloc does not fail) and
+* check that CBMC can model an object of the requested size.
+****************************************************************/
+
+void * safeMalloc( size_t size )
+{
+    __CPROVER_assert( size < CBMC_MAX_OBJECT_SIZE, "safeMalloc size too big" );
+    return nondet_bool() ? NULL : malloc( size );
+}