alternate fix for [#24887] - r33294.

Casting a ray onto an editmesh was building a derivedMesh, raytree, then freeing for every ray-cast.
Noticed while using ruler+snapping in editmode.

Instead of attempting to align the MFace and edit-mesh tessfaces, just use editmesh for ray-casting.


git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@56254 954f8c5b-7b00-dc11-b283-0030488c597c