Backport of PEP 3101, Advanced String Formatting, from py3k.

Highlights:
 - Adding PyObject_Format.
 - Adding string.Format class.
 - Adding __format__ for str, unicode, int, long, float, datetime.
 - Adding builtin format.
 - Adding ''.format and u''.format.
 - str/unicode fixups for formatters.

The files in Objects/stringlib that implement PEP 3101 (stringdefs.h,
unicodedefs.h, formatter.h, string_format.h) are identical in trunk
and py3k.  Any changes from here on should be made to trunk, and
changes will propogate to py3k).

Include/abstract.h

@@ -529,6 +529,13 @@ xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx*/
 
        */
 
+     PyAPI_FUNC(PyObject *) PyObject_Format(PyObject* obj,
+					    PyObject *format_spec);
+       /*
+	 Takes an arbitrary object and returns the result of
+	 calling obj.__format__(format_spec).
+       */
+
 /* Iterators */
 
      PyAPI_FUNC(PyObject *) PyObject_GetIter(PyObject *);