Bugfix: Store width_factor/height_factor per workspace, not per container

This is a relatively big change, however all cases should be handled by
now.

Because the function to do graphical resizing got rather large, I’ve created
a new file src/resize.c for it.

This fixes ticket #35.

include/resize.h

@@ -0,0 +1,27 @@
+/*
+ * vim:ts=8:expandtab
+ *
+ * i3 - an improved dynamic tiling window manager
+ *
+ * (c) 2009 Michael Stapelberg and contributors
+ *
+ * See file LICENSE for license information.
+ *
+ */
+
+#ifndef _RESIZE_H
+#define _RESIZE_H
+
+#include <xcb/xcb.h>
+
+typedef enum { O_HORIZONTAL, O_VERTICAL } resize_orientation_t;
+
+/**
+ * Renders the resize window between the first/second container and resizes
+ * the table column/row.
+ *
+ */
+int resize_graphical_handler(xcb_connection_t *conn, Container *first, Container *second,
+                             resize_orientation_t orientation, xcb_button_press_event_t *event);
+
+#endif