Revert - Merge pull request #962 Fix OpenGL new terrain blend

from BeamNG/fix_opengl_new_terrain_blend (reverted from commit a0d5dc25cd76d0ee5b50f6bada7f1f43ad349562)
3 textures blending fix for OpenGL.
Merge pull request #1005 from BeamNG/revert_terrain_opengl

Revert terrain opengl