Harfbuzz, SDL anf GnuTLS updates

The following projects have been updated:

• Harfbuzz was updated to 1.6.3.
• GnuTLS was updated to 3.5.16.
• SDL was updated to 2.0.7 which now includes support for steam controllers.

Any projects that have a dependency that was updated has also been updated to build with the latest versions of the new libraries as well.