Optimize vector/quaternion Normalize() to a no-op if already at unit length. Changed return value to void.
Optimize cache friendliness of Drawable bounding box update by including the local-space bounding box in the base class. Not used in all subclasses.
Optimize Drawable zone handling by making the zone pointers raw pointers instead of weak. Now finding a drawable's zone can be performed in the threaded view preparation phase.
Removed unnecessary collection of whole visible scene bounding box; it is not used anywhere.


git-svn-id: http://urho3d.googlecode.com/svn/trunk@2512 3bd170d8-ddcf-f82c-f583-7a401ccf5608