xcb: Fix a colormap leak

The function createDummyWindow() allocated a colormap, but never freed
it. Freeing it is safe after the window is created.

Change-Id: I4c876568572c9e1e9dde7047850a51917ef3702f
Signed-off-by: Uli Schlachter <psychon@znc.in>
Reviewed-by: Samuel Rødal <samuel.rodal@digia.com>

src/plugins/platforms/xcb/qglxintegration.cpp

@@ -86,6 +86,7 @@ static Window createDummyWindow(QXcbScreen *screen, XVisualInfo *visualInfo)
                                   0, 0, 100, 100,
                                   0, visualInfo->depth, InputOutput, visualInfo->visual,
                                   CWBackPixel|CWBorderPixel|CWColormap, &a);
+    XFreeColormap(DISPLAY_FROM_XCB(screen), cmap);
     return window;
 }