Add functions PyUnicode_Append() and PyUnicode_AppendAndDel() that mirror
PyString_Concat() and PyString_ConcatAndDel() (the name PyUnicode_Concat()
was already taken).

Change PyObject_Repr() to always return a unicode object.

Update all repr implementations to return unicode objects.

Add a function PyObject_ReprStr8() that calls PyObject_Repr() and converts
the result to an 8bit string.

Use PyObject_ReprStr8() where using PyObject_Repr() can't be done
straightforward.
diff --git a/Include/object.h b/Include/object.h
index f50ffe6..fbeb915 100644
--- a/Include/object.h
+++ b/Include/object.h
@@ -372,6 +372,7 @@
 PyAPI_FUNC(void) _Py_BreakPoint(void);
 PyAPI_FUNC(void) _PyObject_Dump(PyObject *);
 PyAPI_FUNC(PyObject *) PyObject_Repr(PyObject *);
+PyAPI_FUNC(PyObject *) PyObject_ReprStr8(PyObject *);
 PyAPI_FUNC(PyObject *) _PyObject_Str(PyObject *);
 PyAPI_FUNC(PyObject *) PyObject_Str(PyObject *);
 PyAPI_FUNC(PyObject *) PyObject_Unicode(PyObject *);
@@ -418,7 +419,7 @@
 PyAPI_FUNC(long) _Py_HashPointer(void*);
 
 /* Helper for passing objects to printf and the like */
-#define PyObject_REPR(obj) PyString_AS_STRING(PyObject_Repr(obj))
+#define PyObject_REPR(obj) PyString_AS_STRING(PyObject_ReprStr8(obj))
 
 /* Flag bits for printing: */
 #define Py_PRINT_RAW	1	/* No string quotes etc. */