huge change: implement RandR instead of Xinerama

Thanks to Merovius for doing a proof of concept on this one and
being a driving force behind the idea.

Using RandR instead of Xinerama means that we are now able to use
the full potential of the modern way of configuring screens. That
means, i3 now has an idea of the outputs your graphic driver
provides, which allowed us to get rid of the ugly way of detecting
changes in the screen configuration which we used before. Now, your
workspaces should not be confused when changing output modes anymore.

Also, instead of having ugly heuristics to assign your workspaces
to (the screen at position X or the second screen in the list of
screens) you will be able to just specify an output name.

As this change basically touches everything, you should be prepared
for bugs. Please test and report them!

include/xinerama.h

@@ -1,62 +0,0 @@
-/*
- * vim:ts=8:expandtab
- *
- * i3 - an improved dynamic tiling window manager
- *
- * (c) 2009 Michael Stapelberg and contributors
- *
- * See file LICENSE for license information.
- *
- */
-#include "data.h"
-
-#ifndef _XINERAMA_H
-#define _XINERAMA_H
-
-TAILQ_HEAD(screens_head, Screen);
-extern struct screens_head *virtual_screens;
-
-/**
- * Returns true if both screen objects describe the same screen (checks their
- * size and position).
- *
- */
-bool screens_are_equal(i3Screen *screen1, i3Screen *screen2);
-
-/**
- * We have just established a connection to the X server and need the initial
- * Xinerama information to setup workspaces for each screen.
- *
- */
-void initialize_xinerama(xcb_connection_t *conn);
-
-/**
- * This is called when the rootwindow receives a configure_notify event and
- * therefore the number/position of the Xinerama screens could have changed.
- *
- */
-void xinerama_requery_screens(xcb_connection_t *conn);
-
-/**
- * Looks in virtual_screens for the i3Screen whose start coordinates are x, y
- *
- */
-i3Screen *get_screen_at(int x, int y, struct screens_head *screenlist);
-
-/**
- * Looks in virtual_screens for the i3Screen which contains coordinates x, y
- *
- */
-i3Screen *get_screen_containing(int x, int y);
-
-/**
- * Gets the screen which is the last one in the given direction, for example
- * the screen on the most bottom when direction == D_DOWN, the screen most
- * right when direction == D_RIGHT and so on.
- *
- * This function always returns a screen.
- *
- */
-i3Screen *get_screen_most(direction_t direction, i3Screen *current);
-
-#endif