use the static identifier api for looking up special methods

I had to move the static identifier code from unicodeobject.h to object.h in
order for this to work.

Include/object.h

@@ -117,6 +117,35 @@ typedef struct {
 #define Py_TYPE(ob)             (((PyObject*)(ob))->ob_type)
 #define Py_SIZE(ob)             (((PyVarObject*)(ob))->ob_size)
 
+/********************* String Literals ****************************************/
+/* This structure helps managing static strings. The basic usage goes like this:
+   Instead of doing
+
+       r = PyObject_CallMethod(o, "foo", "args", ...);
+
+   do
+
+       _Py_IDENTIFIER(foo);
+       ...
+       r = _PyObject_CallMethodId(o, &PyId_foo, "args", ...);
+
+   PyId_foo is a static variable, either on block level or file level. On first
+   usage, the string "foo" is interned, and the structures are linked. On interpreter
+   shutdown, all strings are released (through _PyUnicode_ClearStaticStrings).
+
+   Alternatively, _Py_static_string allows to choose the variable name.
+   _PyUnicode_FromId returns a borrowed reference to the interned string.
+   _PyObject_{Get,Set,Has}AttrId are __getattr__ versions using _Py_Identifier*.
+*/
+typedef struct _Py_Identifier {
+    struct _Py_Identifier *next;
+    const char* string;
+    PyObject *object;
+} _Py_Identifier;
+
+#define _Py_static_string(varname, value)  static _Py_Identifier varname = { 0, value, 0 }
+#define _Py_IDENTIFIER(varname) _Py_static_string(PyId_##varname, #varname)
+
 /*
 Type objects contain a string containing the type name (to help somewhat
 in debugging), the allocation parameters (see PyObject_New() and
@@ -448,7 +477,7 @@ PyAPI_FUNC(PyObject *) PyType_GenericNew(PyTypeObject *,
                                                PyObject *, PyObject *);
 #ifndef Py_LIMITED_API
 PyAPI_FUNC(PyObject *) _PyType_Lookup(PyTypeObject *, PyObject *);
-PyAPI_FUNC(PyObject *) _PyObject_LookupSpecial(PyObject *, char *, PyObject **);
+PyAPI_FUNC(PyObject *) _PyObject_LookupSpecial(PyObject *, _Py_Identifier *);
 PyAPI_FUNC(PyTypeObject *) _PyType_CalculateMetaclass(PyTypeObject *, PyObject *);
 #endif
 PyAPI_FUNC(unsigned int) PyType_ClearCache(void);