Rework and consolidate monitor handling in MetaScreen

Consolidate all places that deal with output configuration in
MetaScreen, which gets it either from XRandR or from a dummy static configuration.
We still need to read the Xinerama config, even when running xwayland,
because we need the indices for _NET_WM_FULLSCREEN_MONITORS, but
now we do it only when needed.

https://bugzilla.gnome.org/show_bug.cgi?id=705670

src/core/screen-private.h

@@ -38,17 +38,7 @@
 #include <X11/Xutil.h>
 #include "stack-tracker.h"
 #include "ui.h"
-
-typedef struct _MetaMonitorInfo MetaMonitorInfo;
-
-struct _MetaMonitorInfo
-{
-  int number;
-  MetaRectangle rect;
-  gboolean is_primary;
-  gboolean in_fullscreen;
-  XID output; /* The primary or first output for this crtc, None if no xrandr */
-};
+#include "monitor-private.h"
 
 typedef void (* MetaScreenWindowFunc) (MetaScreen *screen, MetaWindow *window,
                                        gpointer user_data);
@@ -100,10 +90,11 @@ struct _MetaScreen
   Window wm_sn_selection_window;
   Atom wm_sn_atom;
   guint32 wm_sn_timestamp;
-  
+
   MetaMonitorInfo *monitor_infos;
-  int primary_monitor_index;
   int n_monitor_infos;
+  int primary_monitor_index;
+  gboolean has_xinerama_indices;
 
   /* Cache the current monitor */
   int last_monitor_index;
@@ -257,4 +248,9 @@ void     meta_screen_workspace_switched (MetaScreen         *screen,
 
 void meta_screen_set_active_workspace_hint (MetaScreen *screen);
 
+int meta_screen_xinerama_index_to_monitor_index (MetaScreen *screen,
+                                                 int         index);
+int meta_screen_monitor_index_to_xinerama_index (MetaScreen *screen,
+                                                 int         index);
+
 #endif