add two generic macros for peeking and setting in the stack

Python/ceval.c

@@ -803,10 +803,12 @@ PyEval_EvalFrameEx(PyFrameObject *f, int throwflag)
 #define SECOND()	(stack_pointer[-2])
 #define THIRD() 	(stack_pointer[-3])
 #define FOURTH()	(stack_pointer[-4])
+#define PEEK(n)         (stack_pointer[-(n)])
 #define SET_TOP(v)	(stack_pointer[-1] = (v))
 #define SET_SECOND(v)	(stack_pointer[-2] = (v))
 #define SET_THIRD(v)	(stack_pointer[-3] = (v))
 #define SET_FOURTH(v)	(stack_pointer[-4] = (v))
+#define SET_VALUE(n, v) (stack_pointer[-(n)] = (v))
 #define BASIC_STACKADJ(n)	(stack_pointer += n)
 #define BASIC_PUSH(v)	(*stack_pointer++ = (v))
 #define BASIC_POP()	(*--stack_pointer)