Doc: Add a cross-referencing label.

htgoebel · htgoebel · commit 3b3ae9aeaa3e · 2017-09-17T00:50:03.000+02:00
This will be used for interlinking from the web-site.

[skip ci]
diff --git a/doc/usage.rst b/doc/usage.rst
@@ -462,6 +462,8 @@ set up the appropriate handlers.
 Platform-specific Notes
 ~~~~~~~~~~~~~~~~~~~~~~~~~~
 
+.. _Platform-specific Notes - Windows:
+
 Windows
 ---------------
 
