Add info about the set API.

Doc/api/refcounts.dat

@@ -1009,6 +1009,25 @@ PySequence_List:PyObject*:o:0:
 PySequence_Tuple:PyObject*::+1:
 PySequence_Tuple:PyObject*:o:0:
 
+PySet_Append:int:::
+PySet_Append:PyObject*:set:0:
+PySet_Append:PyObject*:key:+1:
+
+PySet_Contains:int:::
+PySet_Contains:PyObject*:anyset:0:
+PySet_Contains:PyObject*:key:0:
+
+PySet_Discard:int:::
+PySet_Discard:PyObject*:set:0:
+PySet_Discard:PyObject*:key:-1:no effect if key not found
+
+PySet_Pop:PyObject*::+1:or NULL if key not found
+PySet_Pop:PyObject*:set:0:
+PySet_Pop:PyObject*:key:-1:no effect if key not found
+
+PySet_Size:int:::
+PySet_Size:PyObject*:anyset:0:
+
 PySlice_Check:int:::
 PySlice_Check:PyObject*:ob:0: