[cluttermm] Alpha: Mark this as deprecated.

[Murray Cumming <murrayc src gnome org>]

commit a3939d4968c26d4131c31d57a926efd82ec89e1a
Author: Murray Cumming <murrayc murrayc com>
Date:   Tue Mar 4 23:26:08 2014 +0100

    Alpha: Mark this as deprecated.

 clutter/src/alpha.hg |    6 ++++++
 1 files changed, 6 insertions(+), 0 deletions(-)
---
diff --git a/clutter/src/alpha.hg b/clutter/src/alpha.hg
index d1b291e..173c60e 100644
--- a/clutter/src/alpha.hg
+++ b/clutter/src/alpha.hg
@@ -24,10 +24,16 @@ _PINCLUDE(glibmm/private/object_p.h)
 namespace Clutter
 {
 
+/**
+ * @deprecated For newly written code, it is recommended to use the
+ * "progress-mode" property of Clutter::Timeline, or the 
+ * Clutter::Timeline::set_progress_func() method instead of Clutter::Alpha.
+ */
 class Alpha : public Glib::Object
 {
   _CLASS_GOBJECT(Alpha, ClutterAlpha, CLUTTER_ALPHA, Glib::Object, GObject)
   _DERIVES_INITIALLY_UNOWNED()
+  _IS_DEPRECATED
 
 public:
   /** For instance,