First pass at getting ParaView to compile with OpenGL2

Change-Id: I45f7c317d1488139fd33702cfa33165939b27aa8
Get ParaView working with the OpenGL2 backend

Some more work, it now compiles, links, and even renders some of the
geometry we want much more quickly than before (so long as simple
polygonal rendering is all you really want).

Change-Id: I7fb8ae91451d3a16d7d32f843dc711dfafa106ab
Restore volume rendering - now in VTK master

Change-Id: I104a2776b26ce5786257c0fd73743ef1b9ba13e2
Fix OpenGL legacy backend

Some changes should have been conditional, i.e. added back in for
OpenGL legacy.

Change-Id: I8f4e02fc1267593613b7d5080a57e86d2309f6a2
We have an OpenGL2 vtkCompositeMapper2 now

Remove some of the ifdefs definding 1 to 2, use the new mapper.

Change-Id: I80186e3f05a09b435f4353843302ace84261ce4d
Merge topic 'opengl2-backend' into next

dfcfbaf8 We have an OpenGL2 vtkCompositeMapper2 now
2d67dfad Fix OpenGL legacy backend
44b1d8e9 Restore volume rendering - now in VTK master
caee75a6 Get ParaView working with the OpenGL2 backend
69a9c54f First pass at getting ParaView to compile with OpenGL2