wayland: Update copyright header information

Update copyright information to include the creators of the wayland video driver,
Joel Teichroeb and Benjamin Franzke.
Fix typo

Thanks to Ryan C. Gordon for pointing this out.
wayland: Fix pumpevents to actually read from fd when it has data
wayland: Fix crash when making a NULL SDL_Window current
wayland: Set opaque region for window

Important optimization hint to let compositors clip away content below
the SDL window or scan out from an SDL window.
Merge branch 'wayland' of github.com:soreau/SDL into wayland.fix_4