Added config key for default orientation of containers (new_container_orientation) and added support in randr.c for automatically changing the orientation when user does a xrandr rotate.

include/config.h

@@ -95,6 +95,9 @@ struct Config {
         int container_stack_limit;
         int container_stack_limit_value;
 
+        /** Default orientation for new containers */
+        int default_orientation;
+
         /** By default, focus follows mouse. If the user explicitly wants to
          * turn this off (and instead rely only on the keyboard for changing
          * focus), we allow him to do this with this relatively special option.