devices: Make MetaDevice/MetaDeviceMap partly public

MetaDevice is quite limited outside of the core, mostly useful
to represent a device, and get the paired one.

src/core/display.c

@@ -48,7 +48,7 @@
 #include "xprops.h"
 #include "workspace-private.h"
 #include "bell.h"
-#include "device.h"
+#include "device-private.h"
 #include "input-events.h"
 #include <meta/compositor.h>
 #include <X11/Xatom.h>
@@ -5511,3 +5511,19 @@ meta_display_get_leader_window (MetaDisplay *display)
 {
   return display->leader_window;
 }
+
+/**
+ * meta_display_get_device_map:
+ * @display: a #MetaDisplay
+ *
+ * Returns the MetaDeviceMap used to handle the display devices.
+ *
+ * Returns: (transfer none): The display's #MetaDeviceMap
+ **/
+MetaDeviceMap *
+meta_display_get_device_map (MetaDisplay *display)
+{
+  g_return_val_if_fail (META_IS_DISPLAY (display), NULL);
+
+  return display->device_map;
+}