AP_HAL: implement standard realloc method

libraries/AP_HAL/Util.h

@@ -159,8 +159,10 @@ public:
     // heap functions, note that a heap once alloc'd cannot be dealloc'd
     virtual void *allocate_heap_memory(size_t size) = 0;
     virtual void *heap_realloc(void *heap, void *ptr, size_t new_size) = 0;
+    virtual void *std_realloc(void *ptr, size_t new_size) { return realloc(ptr, new_size); }
 #endif // ENABLE_HEAP
 
+
     /**
        how much free memory do we have in bytes. If unknown return 4096
      */