Remove libappindicator support.

Index: src/gromit-mpx.h
--- src/gromit-mpx.h.orig
+++ src/gromit-mpx.h
@@ -28,11 +28,6 @@
 #include <glib.h>
 #include <gdk/gdk.h>
 #include <gtk/gtk.h>
-#ifdef APPINDICATOR_IS_LEGACY
-#include <libappindicator/app-indicator.h>
-#else
-#include <libayatana-appindicator/app-indicator.h>
-#endif
 
 #define GROMIT_MOUSE_EVENTS ( GDK_BUTTON_MOTION_MASK | \
                               GDK_BUTTON_PRESS_MASK | \
@@ -102,7 +97,6 @@ typedef struct
 typedef struct
 {
   GtkWidget   *win;
-  AppIndicator *trayicon;
 
   GdkCursor   *paint_cursor;
   GdkCursor   *erase_cursor;