patch 9.1.1485: missing Wayland clipboard support

Problem:  missing Wayland clipboard support
Solution: make it work (Foxe Chen)

fixes: #5157
closes: #17097

Signed-off-by: Foxe Chen <chen.foxe@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/feature.h b/src/feature.h
index 56d1958..07db96c 100644
--- a/src/feature.h
+++ b/src/feature.h
@@ -813,6 +813,14 @@
 #endif
 
 /*
+ * +wayland		Unix only.  Include code for the wayland protocol,
+ *                      only works if HAVE_WAYLAND is defined.
+ */
+#if defined(FEAT_NORMAL) && defined(UNIX)
+# define WANT_WAYLAND
+#endif
+
+/*
  * XSMP - X11 Session Management Protocol
  * It may be preferred to disable this if the GUI supports it (e.g.,
  * GNOME/KDE) and implement save-yourself etc. through that, but it may also
@@ -912,6 +920,14 @@
 # endif
 #endif
 
+#if defined(FEAT_NORMAL) && defined(UNIX) \
+    && defined(HAVE_WAYLAND) && defined(WANT_WAYLAND)
+# define FEAT_WAYLAND_CLIPBOARD
+# ifndef FEAT_CLIPBOARD
+#  define FEAT_CLIPBOARD
+# endif
+#endif
+
 /*
  * +dnd		Drag'n'drop support.  Always used for the GTK+ GUI.
  */