ENH: Added new vtkOpenGLGPUVolumeRayCastMapper to VolumeOpenGL2

Change-Id: I18f57a2de604ee6aaf760e8868e32d0802c9fe32
ENH: Add all GPURayCast tests for OpenGL2 backend

If OpenGL2 backend is selected, only and all the GPURayCast tests are enabled.
If VolumeOpenGLNew is selected, all GPURayCast along with other VolumeOpenGL
tests are enabled.

Change-Id: Ia571fe10a1c0ac05df6433278190e7f108768a7c
Remove unused shader files

Change-Id: I835c20c7209f46f8f18bc2611a19eb7e403e1746
Fix cmake string issue

Change-Id: Ib71d353972800ba6f62133f98384a55ceb915013
Merge branch 'master' into opengl2_volumerendering

Conflicts:
	Rendering/Volume/Testing/Cxx/CMakeLists.txt
	Rendering/Volume/module.cmake

Change-Id: I4feb7d3b896f76a51e2b83ead3b15d478d79888e
Merge remote-tracking branch 'origin/master' into opengl2_volumerendering

Change-Id: I38a955b3be37fbabdedb809676fa1a402f40c10b
Fix compiler error

No clue how that got through.

Change-Id: Ib0a6ed7eca4dd5f58edbb31e3a190d242e2fdc93
Merge topic 'wtf' into master

4b6c88a3 Fix compiler error
Merge remote-tracking branch 'origin/master' into opengl2_volumerendering

Change-Id: I03b6e2c3ac544593c68f419859375bcd4ef7589b
Fix issue with mesa and gl_FrontFacing

This fix seems to work on both Mac and Mesa. It should be good
on all other platforms as well. Also did some indentation cleanup.
The only real change was changing

  if (int(gl_FrontFacing) == 0)

to

  if (gl_FrontFacing == false)

Change-Id: If4270f1a87ae495445dffd8af72fee1bfa0f2011
Fixed warnings with shadowed variables.

Change-Id: I20281b1a3968db365404c6b4d56372236548ae11
Merge topic 'mesa_lighting_fix' into master

221ba52d Fix issue with mesa and gl_FrontFacing
Merge topic 'fix_extract_thresholds_for_table' into master

ef663ee2 Fixed warnings with shadowed variables.
make it so that this test works on the old OpenGL backend

For the old OpenGL we use the extension manager to check for Mesa
and return true. Mesa seems to be broken for this feature. On the new
OpenGL2 we should be fine as it is handled in our code.

Change-Id: I2ef97b7acc7977aa6b0e60f5182d4ffc7848ae7e
Merge topic 'edge_flag_test_fix' into master

7ac000fa make it so that this test works on the old OpenGL backend
Merge topic 'opengl2_volumerendering' into master

0405aab2 Merge remote-tracking branch 'origin/master' into opengl2_volumerendering
26962bf1 Merge remote-tracking branch 'origin/master' into opengl2_volumerendering
2366f21e Merge branch 'master' into opengl2_volumerendering
3647b663 Fix cmake string issue
92413fb1 Remove unused shader files
bcc16268 ENH: Add all GPURayCast tests for OpenGL2 backend
09ae2a3c ENH: Added new vtkOpenGLGPUVolumeRayCastMapper to VolumeOpenGL2
Fix a MTime check in the matrix cache

Change-Id: I3882887b8d688534171837a00d08c46c6a8ac67d
Merge topic 'actor_fix' into master

7a7004c9 Fix a MTime check in the matrix cache
Fix header test warning

Change-Id: I4b406381455eb0188de1ffe43c4036eb44522865
Merge topic 'minor_fix' into master

b6d4561a Fix header test warning