SDL2_ttf: update to 2.20.0
SDL2_ttf: update to 2.20.0

* Change source URL to GitHub project.
* Add pgp key to validate source tarball.
* Remove upstream patches.
stahta01/MINGW-packages,fabiangreffrath/MINGW-packages,oscarfv/MINGW-packages,lhmouse/MINGW-packages,lhmouse/MINGW-packages,fabiangreffrath/MINGW-packages,oscarfv/MINGW-packages,oscarfv/MINGW-packages,lhmouse/MINGW-packages,JPeterMugaas/MINGW-packages,oroppas/MINGW-packages,oroppas/MINGW-packages,JPeterMugaas/MINGW-packages,lhmouse/MINGW-packages,JPeterMugaas/MINGW-packages,fabiangreffrath/MINGW-packages,stahta01/MINGW-packages,oroppas/MINGW-packages,oscarfv/MINGW-packages,oroppas/MINGW-packages,JPeterMugaas/MINGW-packages,JPeterMugaas/MINGW-packages,stahta01/MINGW-packages,stahta01/MINGW-packages,fabiangreffrath/MINGW-packages,lhmouse/MINGW-packages,oroppas/MINGW-packages,fabiangreffrath/MINGW-packages,fabiangreffrath/MINGW-packages,oroppas/MINGW-packages,oscarfv/MINGW-packages,stahta01/MINGW-packages,stahta01/MINGW-packages,lhmouse/MINGW-packages,JPeterMugaas/MINGW-packages,oscarfv/MINGW-packages