Added ws_wayland_buffer_release
Added frame callback implementation to support changing buffers
Added null check against surface from wayland
Removed the + 8 modifier from keycodes

This is something the client should do it seems. `weston-terminal` at least
seems to expect non offsetted key events... For the moment we have no choice but
to trust their code.
Removed double keyboard handle
Added modifiers to keyboard
Merge pull request #498 from TheNeikos/fix-wayland_client_interaction

Fix wayland client interaction