Fixing and upgrading some games SlackBuild. Visiting 0ad and 0ad-data after
long time abandonned.
* 0ad-data: Upgraded to version 0.0.12.
* 0ad: Upgraded to version 0.0.12. Add OpenAL, enet, nvtt, and wxWidgets
    to slack-required.
* SDL_image: Added version 1.2.12. Needed by fife.
* SDL_ttf: Added version 2.0.11. Needed by fife.
* fife: Added version 0.3.4. This is game engine for unknown-horizons.
* guichan: Added version 0.8.2. Needed by fife.
* nvtt: Updated SlackBuild script. Added some patch from 0ad with some
    modification. Linked to cg.
* pyyaml: Added version 3.10. Needed by unknown-horizons.
* scons: Upgraded to version 2.3.0.
* speed-dreams: Added version 2.0.0.
* unknown-horizons: Added version 2013.1

As always, read the slack-required for dependency information.