This drops the "feature" to load level 0 from the custom texture
and all other levels from the native one if the size matches.
But in my opinion, when a custom texture only provide one level,
no more should be used at all.
If the host device supports GLES 3.1 and AEP we can have stereo rendering.
Just need to make sure to grab the correct function pointer that GL_EXT_geometry_shader provides, and enable AEP in the shaders.
We can't just check if AEP is in the extension list for support because Qualcomm has failed once more.
With the Nexus 6 it reports support for AEP but doesn't support OpenGL ES 3.1, which is an impossible combination.
From reports on their forum it seems that attempting to use any AEP things results in nothing happening, seems like a stub implementation.
GLSL ES 3.10 adds implicit support for the binding layout qualifier that we use.
Changes our GLSL version enums to bit values so we can check for both ES versions easily.
