GeometryShaderGen: Pack uniforms more tightly.
VertexManager: Disable culling for lines and points.
GeometryShaderGen: Cosmetics.
GeometryShader: Disable the geometry shader stage if it is a pass-through shader.
VideoCommon: Pass interface blocks between shader stages to resolve naming conflicts.
OGL: Don't generate a geometry shader if the backend doesn't support it.

This commit repurposes the bSupportsStereoscopy flag as the bSupportsGeometryShaders flag.
D3D: Set the geometry shader before every draw call.

And refactor the VertexManager draw call.
GeometryShaderManager: Set the constants within the callbacks.
VideoCommon: Only use interface blocks when geometry shaders are supported.
D3D: Use ROUND_UP macro for rounding buffer sizes.
OGL: Check OpenGL version for geometry shader support.
VideoCommon: Don't pass structs between shader stages when geometry shaders are unsupported.