Restore Netsurf port

ToaruOS once had a port of Netsurf, circa 2016. We should bring that back.

Netsurf has some dependencies which don't exist in the current port catalog:

• Curl, which builds with some minor patches, including support for mbedtls.
• zlib, which shouldn't have any issues, it was just largely obviated by toaru_inflate.
• libpng, again, was obviated by toaru_png; I'd rather not rewrite things to use our libraries, so just porting these is worthwhile.
• Freetype, which was working in Toaru 1.14.
• libjpeg, which is optional but desirable; our JPEG parser is insufficient for most images on the Internet anyway.

During the last port of Netsurf, we did not have a BSD sockets layer and the Curl port was largely stubbed, so I'm not sure we were ever even able to load web pages, just local files on disk. I expect things will go a bit better this time around.

The framebuffer backend for Netsurf supports SDL, and the first pass at porting Netsurf should use it. A future improvement might be to write a native Yutani frontend - possibly one that makes use of our menu and button libraries.