status: document the content of the returned tuple in the docstring

The ``status`` function returns a lot of information. We document it.

mercurial/context.py

@@ -275,6 +275,8 b' class basectx(object):'
         directory.
 
         If other is None, compare this node with working directory.
+
+        returns (modified, added, removed, deleted, unknown, ignored, clean)
         """
 
         ctx1 = self