Add -3 option to the interpreter to warn about features that are
deprecated and will be changed/removed in Python 3.0.

This patch is mostly from Anthony.  I tweaked some format and added
a little doc.
diff --git a/Objects/dictobject.c b/Objects/dictobject.c
index 7d6ff61..daf64e0 100644
--- a/Objects/dictobject.c
+++ b/Objects/dictobject.c
@@ -1688,7 +1688,7 @@
  }
 
 static PyObject *
-dict_has_key(register dictobject *mp, PyObject *key)
+dict_contains(register dictobject *mp, PyObject *key)
 {
 	long hash;
 	dictentry *ep;
@@ -1706,6 +1706,16 @@
 }
 
 static PyObject *
+dict_has_key(register dictobject *mp, PyObject *key)
+{
+	if (Py_Py3kWarningFlag &&
+	    PyErr_Warn(PyExc_DeprecationWarning, 
+		       "dict.has_key() not supported in 3.x") < 0)
+		return NULL;
+	return dict_contains(mp, key);
+}
+
+static PyObject *
 dict_get(register dictobject *mp, PyObject *args)
 {
 	PyObject *key;
@@ -1978,7 +1988,7 @@
 "D.iteritems() -> an iterator over the (key, value) items of D");
 
 static PyMethodDef mapp_methods[] = {
-	{"__contains__",(PyCFunction)dict_has_key,      METH_O | METH_COEXIST,
+	{"__contains__",(PyCFunction)dict_contains,      METH_O | METH_COEXIST,
 	 contains__doc__},
 	{"__getitem__", (PyCFunction)dict_subscript,	METH_O | METH_COEXIST,
 	 getitem__doc__},