Added a --global-module-index option to specify a (possibly relative) URL
to the Global Module Index for a set of documents.  This is used to include
a reference to the global index from the per-document module indexes, so
that it is just a little easier to find.

(Someone suggested this, but I do not remember who.  Please let me know if
it was you -- thanks!)
diff --git a/Doc/html/Makefile b/Doc/html/Makefile
index 6b2827b..5da7cab 100644
--- a/Doc/html/Makefile
+++ b/Doc/html/Makefile
@@ -14,7 +14,8 @@
 WEBCHECKER=$(PYTHON) $(TOPDIR)/../Tools/webchecker/webchecker.py
 MKHOWTO=   $(TOOLSDIR)/mkhowto --about $(TOPDIR)/html/stdabout.dat \
 		--address $(PYTHONDOCS) --up-link ../index.html \
-		--up-title "Python Documentation Index"
+		--up-title "Python Documentation Index" \
+		--global-module-index "../modindex.html"
 MKHTML=	   $(MKHOWTO) --html
 
 BUILDINDEX=$(TOOLSDIR)/buildindex.py