First stab at NETWM system tray support

[Mike Hearn]

OK, so rereading this patch in the morning when I'm feeling more awake,
I can see a few mistakes that slipped past my review last night. To save
people the hassle of point them out to me, here they are:

1) The whole of X11DRV_systray_dock_window should probably be protected
with a TS lock, instead of just the middle section.

2) The line: X11DRV_systray_dock_window(display, undockedTrayIcons[0])
should use (undockedTrayIconsCount - 1) as the index, not 0.

3) Whitespace noise in the part that sets the KDE hints

4) Commented out line I used for debugging made its way into the patch.

5) This confuses me:

- ... create_desktop( Display *display, WND *wndPtr )
+ ... create_desktop( Display *display, WND *wndPtr, CREATESTRUCTA *cs )
+     SendMessageW( wndPtr->hwndSelf, WM_NCCREATE, 0, (LPARAM)cs );

as I don't remember writing that code.

Presumably the createstruct parameter was there when I first wrote the
patch and removed later without me noticing, as I diffed the tree in a
different location to where I wrote it, CVS thought I readded it. So I
guess this is "old code" noise.

I'll try again tonight.

-- 
Mike Hearn <m.hearn at signal.qinetiq.com>
QinetiQ - Malvern Technology Center