The VTOL code modifications have been ported to MultiWii V1.8 patch 2. There are two VTOL airframe definitions: VTOL_TAIL for your typical tricopter style airframe with tail yaw control, and VTOL_DUAL for individually tilting front motors for yaw control. I have only tested the VTOL_DUAL definition. Some control directions may be need to be changed based on your servo orientations.
EDIT: Code has been simplified, and a VTOL_QUADX model has been built.
EDIT2: Fixed some typos, slowed down raising of flaps.