Rename operator TEST_EMPTY into EMPTY_P to be compliant with iterator operator

m-buffer.h

@@ -1170,7 +1170,7 @@ M_C(name, _init)(buffer_t v, size_t size)                                     \
    ,PUSH(M_C(name,_push))                                                     \
    ,POP(M_C(name,_pop))                                                       \
    ,OPLIST(oplist)                                                            \
-   ,TEST_EMPTY(M_C(name, _empty_p)),                                          \
+   ,EMPTY_P(M_C(name, _empty_p)),                                             \
    ,GET_SIZE(M_C(name, _size))                                                \
    )