Created by: CrossVR
This reverts commit 74b862f6, reversing changes made to 7efe1437.
This effectively removes the incomplete OpenGL backend.
Development on the OpenGL backend has been abandoned in favor of creating a Vulkan backend. The Vulkan backend will become the preferred backend for all platforms, therefore I will call it the R5 renderer. This will also solve the renderer preference problem that the OpenGL backend had.
The Vulkan backend will make use of the HLSL frontend for glslang, so the GLSL shaders are no longer required.