hhctrl.ocx: Don't show unimplemented buttons.

[Owen Rudge]

> Could you point me to a link on this behavior?  I'm pretty sure that
> many of these buttons send a signal that applications can hook into
> and override the default (do-nothing) behavior.

The documentation for those specific values appears to be non-existent - 
the latest (as far as I'm aware) HTML Help documentation can be found here:

http://www.microsoft.com/download/en/details.aspx?id=21138

Additionally, as Francois mentioned, the HTML Help header files do 
include some references to unimplemented functionality.

-- 
Owen Rudge
http://www.owenrudge.net/