the event header seemingly being generic with libevent thus renaming it.
openal and opengl are deprecated on newer mac os releases thus suppressing the build warnings.
Makes the liquid waving shader per-nodedef like waving leaves/plants,
instead of being applied to all liquids.
Like the waving leaves/plants shaders, the liquid waving shader can
also be applied to meshes and nodeboxes.
Derived from a PR by t0ny2.
