EGL: Better wayland detection in eglGetDisplay

The problem with using dlsym to look for wl_display_interface is that variables by that name are emitted into other client libraries besides libwayland-client. libSDL2 has this property, at least. Instead of that, use dladdr() to look up the name of the symbol pointed to, and accept any symbol with the right name as being wayland enough.

Signed-off-by: Adam Jackson ajax@redhat.com