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).
diff --git a/Include/abstract.h b/Include/abstract.h
index a432a65..c61cc8b 100644
--- a/Include/abstract.h
+++ b/Include/abstract.h
@@ -529,6 +529,13 @@
 
        */
 
+     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 *);
diff --git a/Include/formatter_string.h b/Include/formatter_string.h
new file mode 100644
index 0000000..14c4811
--- /dev/null
+++ b/Include/formatter_string.h
@@ -0,0 +1,12 @@
+PyObject *
+string__format__(PyObject *self, PyObject *args);
+
+PyObject *
+string_long__format__(PyObject *self, PyObject *args);
+
+PyObject *
+string_int__format__(PyObject *self, PyObject *args);
+
+PyObject *
+string_float__format__(PyObject *self, PyObject *args);
+
diff --git a/Include/formatter_unicode.h b/Include/formatter_unicode.h
new file mode 100644
index 0000000..51406ab
--- /dev/null
+++ b/Include/formatter_unicode.h
@@ -0,0 +1,12 @@
+PyObject *
+unicode__format__(PyObject *self, PyObject *args);
+
+PyObject *
+unicode_long__format__(PyObject *self, PyObject *args);
+
+PyObject *
+unicode_int__format__(PyObject *self, PyObject *args);
+
+PyObject *
+unicode_float__format__(PyObject *self, PyObject *args);
+