EGL_MESA_screen_surface version 6

[Jon Smirl]

What about opaque screen handles?

  EGLBoolean eglGetScreensMESA(EGLDisplay dpy,
                             EGLScreen *screens, EGLint screens_size,
                             EGLint *num_screens)

For all functions replace EGLint screen_number with EGLScreen screen

All functions that deal with these objects can return these errors:
  EGL_LOST_SCREEN_MESA
  EGL_LOST_MODE_MESA
  EGL_LOST_SURFACE_MESA

And note that handle reuse should be avoided if possible to stop stale
handles from being confused with new ones.

-- 
Jon Smirl
jonsmirl at gmail.com