-Fixed bugs in new 'blend operation' code, the 'if' checks on EBO_NONE could never return true, so everything was set to blend

-Fixed performance bug in CTerrainSceneNode, noticed that preRenderLODCalculations() is ran every render, instead of just when LOD data is recalculated.
  This increases the frame-rate on 'Terrain Rendering Example 12' from 410fps to 1300fps on my machine.




git-svn-id: svn://svn.code.sf.net/p/irrlicht/code/trunk@3728 dfc29bdd-3216-0410-991c-e03cc46cb475