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/Objects/boolobject.c b/Objects/boolobject.c
index f98af9f..0a9f958 100644
--- a/Objects/boolobject.c
+++ b/Objects/boolobject.c
@@ -24,10 +24,10 @@
 
 	if (self == Py_True)
 		s = true_str ? true_str :
-			(true_str = PyString_InternFromString("True"));
+			(true_str = PyUnicode_FromString("True"));
 	else
 		s = false_str ? false_str :
-			(false_str = PyString_InternFromString("False"));
+			(false_str = PyUnicode_FromString("False"));
 	Py_XINCREF(s);
 	return s;
 }