egl: add test for EGL_KHR_display_reference
Mesa implementation: mesa!10118
WIP
because it doesn't work yet; I'm currently getting a segfault in glvnd, I'll need to investigate that (starting with a debug build of glvnd so that I can see where it segfaults), but I ran out of time to work on it this weekend so I'm posting this test as is.
(cc @lynxeye)
Edited by Eric Engestrom