[gtkmm-documentation] Adapt to SeatCapabilities as Seat::Capabilities.

[Murray Cumming <murrayc src gnome org>]

commit aac006abe8e9c0534063208e96f1f47b3dbed570
Author: Murray Cumming <murrayc murrayc com>
Date:   Wed May 3 10:33:12 2017 +0200

    Adapt to SeatCapabilities as Seat::Capabilities.

 .../others/cellrenderercustom/cellrendererpopup.cc |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/examples/others/cellrenderercustom/cellrendererpopup.cc 
b/examples/others/cellrenderercustom/cellrendererpopup.cc
index 6e948b8..f75cd5a 100644
--- a/examples/others/cellrenderercustom/cellrendererpopup.cc
+++ b/examples/others/cellrenderercustom/cellrendererpopup.cc
@@ -31,7 +31,7 @@ bool grab_on_window(const Glib::RefPtr<Gdk::Window>& window)
   {
     auto seat = device->get_seat();
     if (seat &&
-        seat->grab(window, Gdk::SeatCapabilities::ALL, true) == Gdk::GrabStatus::SUCCESS)
+        seat->grab(window, Gdk::Seat::Capabilities::ALL, true) == Gdk::GrabStatus::SUCCESS)
       return true;
   }