Blender Git Loki

Enable again write depth pass for strokes only

Remove write zdepth to avoid z-fighting

The strokes don't need to write the depth buffer

Merge branch 'blender2.8' into greasepencil-object

Cleanup: Change some xray strings and parameter names

Cleanup: Remove unused code

THis code has been ported to new shaders

Implement Xray mode for strokes

Now support 3 modes: Front, 3D space and Back.

Still some problems with zfighting with layers that need to be fixed

Use zdepth of the position in geometry shader

Merge branch 'blender2.8' into greasepencil-object

Add more control for debug lines

Now the debug lines are only visible when code is 668

Merge branch 'blender2.8' into greasepencil-object

Separate zdepth to function to use in future

Now, the value is fixed but need to be calculated.

Cleanup unused code

Add debug information

Add set cache to dirty when Gpencil is update in several places

Remove old opengl code

Remove zdepth check for Drawing buffer

The drawing buffer and edit point must be always visible

Enable zdepth for passes.

Actually only works for filling

Merge branch 'blender2.8' into greasepencil-object

Remove old opengl code in shaders

Remove check on back of camera

This check is getting weird result and create a segfault in the cache due changes in the index of the stroke depending of point of view.

Need to have a better implementation. We keep disabled while we found a better solution that not change the index of the strokes (maybe separate this check and add to cache_idx anyway)