Add a simple client for testing compositor damage handling

Add a simple client for testing compositor damage handling

This allows for easily testing a compositor's damage tracking in all
currently available configurations including wl_surface.buffer_transform,
wl_surface.buffer_scale, and wl_viewport.  It also includes a
--rotating-damage that flag instructs the client to change the
wl_surface.buffer_transform on every commit.  This tests the compositor for
proper handling of texture uploads even when the transform has changed but
the buffer size hasn't.