egl/x11: Honor the EGL_PLATFORM_X11_SCREEN_EXT attribute

Introduce _egl_display::Options::Platforms for private storage.
For X11 platforms we can use it for the screen number as set by
EGL_PLATFORM_X11_SCREEN_EXT.

Reviewed-by: Eric Anholt <eric@anholt.net>
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>
Signed-off-by: Adam Jackson <ajax@redhat.com>
3 files changed