Revise the __all__ index entry a touch.
diff --git a/Doc/ref/ref6.tex b/Doc/ref/ref6.tex
index e6b3246..9c088e9 100644
--- a/Doc/ref/ref6.tex
+++ b/Doc/ref/ref6.tex
@@ -703,7 +703,7 @@
defined, the set of public names includes all names found in the
module's namespace which do not begin with an underscore character
(\character{_}).
-\index{__all__}
+\withsubitem{(optional module attribute)}{\ttindex{__all__}}
The \keyword{from} form with \samp{*} may only occur in a module
scope. If the wild card form of import --- \samp{import *} --- is