egl: wayland: Avoid a crash that is likely some race condition

Dispatching the wayland queue in WaylandNativeWindow destructor avoids
a crash that seems to happen when the window is first destroyed and quickly
re-created (eg. startup resize).
Merge pull request #137 from kvahlman/destoyer-of-worlds

egl: wayland: Avoid a crash that is likely some race condition
Merge pull request #136 from groleo/master

use EGL_TEXTURE_EXTERNAL_WL
eglQueryWaylandBufferWL: drop EGL_TEXTURE_Y_UV_WL

using EGL_TEXTURE_Y_UV_WL will also require EGL_WAYLAND_PLANE_WL,
but we don't support EGL_WAYLAND_PLANE_WL.

Signed-off-by: Adrian Negreanu <adrian.m.negreanu@intel.com>