egl/wayland: Don't invalidate drawable on swap buffers

egl/wayland: Don't invalidate drawable on swap buffers

We used to invalidate the drawable after a call to eglSwapBuffers(),
so that a wl_egl_window_resize() would take effect for the next frame.
However, that leads to calling dri2_get_buffers() when eglMakeCurrent()
is called with the current context and surface, and a later call to
wl_egl_window_resize() would not take effect until the next buffer
swap.

Instead, add a callback from wl_egl_window_resize() back to the wayland
egl platform, and invalidate the drawable only when it is resized.

This solves a bug on wayland clients when going back to windowed mode
from fullscreen when clicking a pop up menu, where the window size
after this would be the fullscreen size.

Note: this is a candidate for stable branches.
CC: wayland-devel@lists.freedesktop.org