ProjectVector method was modifying plane normal.

Thanks to David Jarvis for pointing out this bug.  Projecting a vector
would cause the plane's normal to be multiplied by the dotprod of the
plane and the vector (in some cases, causing the normal to become zero).
Obviously the ProjectVector() function should not modify the normal.

Change-Id: Idaa86fdad897777a65fba6f8ac5309a3582175e6
Merge topic 'plane-project-vector' into master

ba3c24c3 ProjectVector method was modifying plane normal.