Implement floating (please test and find bugs)

Details which are missing: A command to hide/show all floating clients,
moving/resizing clients with your mouse holding Mod1 (click anywhere
in the client, not just on its borders), resize/move by keyboard, select
next/previous client by keyboard

include/layout.h

@@ -36,6 +36,18 @@ void decorate_window(xcb_connection_t *conn, Client *client, xcb_drawable_t draw
  */
 void redecorate_window(xcb_connection_t *conn, Client *client);
 
+/**
+ * Pushes the client’s x and y coordinates to X11
+ *
+ */
+void reposition_client(xcb_connection_t *conn, Client *client);
+
+/**
+ * Pushes the client’s width/height to X11 and resizes the child window
+ *
+ */
+void resize_client(xcb_connection_t *conn, Client *client);
+
 /**
  * Renders the given container. Is called by render_layout() or individually (for example
  * when focus changes in a stacking container)