LwjglRenderer - Preparing for abstraction layer shift
 * All GL calls are done via static imports
 * Once again remove dependency on GL21 / GL30 - with the generator it will be possible to choose whether to target GL2+extensions or GL3 core
 * ContextCapabilities is field in Renderer, not allowed to use GLContext to retrieve it anymore
 * Assume depth textures are always supported (they should be since GL1.4)