Usability

- Cycles materials now render in Blender Internal too, skipping the nodes.
  Not very useful, but at least things then show up on renders and in
  previews.

- Node editor: if wrong shader nodes are in a tree, they draw with thene
  color RED ALERT headers now. (Switching render engine will show it).



git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@54081 954f8c5b-7b00-dc11-b283-0030488c597c