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.

Modules/_hashopenssl.c

@@ -221,7 +221,7 @@ EVP_repr(PyObject *self)
     char buf[100];
     PyOS_snprintf(buf, sizeof(buf), "<%s HASH object @ %p>",
             PyString_AsString(((EVPobject *)self)->name), self);
-    return PyString_FromString(buf);
+    return PyUnicode_FromString(buf);
 }
 
 #if HASH_OBJ_CONSTRUCTOR