dirs: port PyInt code to work on Python 3

PyIntObject no longer exists in Python 3. Instead, there is
PyLongObject.

Furthermore, PyInt_AS_LONG is a macro referencing a struct member.
PyInt_AS_LONG doesn't exist in Python 3 and PyLong_AS_LONG is a
#define for PyLong_AsLong, which is a function. So assigning to the
return value of PyLong_AS_LONG doesn't work.

This patch introduces a macro for obtaining the value of an
integer-like type that works on Python 2 and Python 3. On
Python 3, we access the struct field of the underlying
PyLongObjet directly, without overflow checking. This is
essentially the same as what Python 2 was doing except using a
PyLong instead of a PyInt.

mercurial/dirs.c

@@ -11,6 +11,12 b''
 #include <Python.h>
 #include "util.h"
 
+#ifdef IS_PY3K
+#define PYLONG_VALUE(o) ((PyLongObject *)o)->ob_digit[1]
+#else
+#define PYLONG_VALUE(o) PyInt_AS_LONG(o)
+#endif
+
 /*
  * This is a multiset of directory names, built from the files that
  * appear in a dirstate or manifest.
@@ -66,17 +72,21 b' static int _addpath(PyObject *dirs, PyOb'
 
 		val = PyDict_GetItem(dirs, key);
 		if (val != NULL) {
-			PyInt_AS_LONG(val) += 1;
+			PYLONG_VALUE(val) += 1;
 			break;
 		}
 
 		/* Force Python to not reuse a small shared int. */
+#ifdef IS_PY3K
+		val = PyLong_FromLong(0x1eadbeef);
+#else
 		val = PyInt_FromLong(0x1eadbeef);
+#endif
 
 		if (val == NULL)
 			goto bail;
 
-		PyInt_AS_LONG(val) = 1;
+		PYLONG_VALUE(val) = 1;
 		ret = PyDict_SetItem(dirs, key, val);
 		Py_DECREF(val);
 		if (ret == -1)
@@ -113,7 +123,7 b' static int _delpath(PyObject *dirs, PyOb'
 			goto bail;
 		}
 
-		if (--PyInt_AS_LONG(val) <= 0) {
+		if (--PYLONG_VALUE(val) <= 0) {
 			if (PyDict_DelItem(dirs, key) == -1)
 				goto bail;
 		} else