egl: implement Haiku driver over Gallium, drop old HGL
Make EGL actually functional on Haiku and use it with conjunction to glvnd
driver loader instead of Haiku custom HGL driver loader.
BitmapHook is currently used as EGL window surface. It is a temporary solution until proper Haiku windowing system integration API will be designed.
This EGL implementation works directly on to of Gallium and it don't use DRI layer. I would like to hear suggestions about Gallium integration code improvements/fixes.
Depends on !21110 (merged)