It contains a few (un)packing functions present in ARB_gpu_shader5, but
isn't mentioned anywhere except GLSL 4.20 changelog (and there it has
its old name, ARB_shading_language_pack2f). It might be supported on
machines where ARB_gpu_shader5 can't be supported (GL3 HW).
Separated EXT_framebuffer_object, EXT_framebuffer_blit,
EXT_framebuffer_multisample and EXT_packed_depth_stencil don't have the
same functionality as ARB_framebuffer_object (e.g. missing
GL_FRAMEBUFFER_UNDEFINED in glCheckFramebufferStatus()) and separated
read/draw binding is only in EXT_framebuffer_blit, which complicates the
internals.
Checked with Mesa 8/9 and OpenGL 2.1, current one has
ARB_framebuffer_object and also all these four, Mesa 7.7 didn't have
EXT_framebuffer_multisample, but that's a long time ago, so not
supporting these separate extensions shouldn't be an issue.
The problem with unavailable separate binding points remains on OpenGL
ES 2.0, there are three different extensions bringing that
functionality, thus the code managing the available binding points
remains there.
Robust *Framebuffer::read() access, ability to query robust buffer
access behavior in Context::flags(), ability to check graphics reset
status and reset notification policy in Renderer.
OpenGL 3.0 specification is awesomely confused with extensions. The ones
listed in specs don't have the complete functionality and references
to related ARB extensions are nowhere to be found.