Ported my #audiovisual https://mathr.co.uk/puzzle to empd, not published it formally yet...

With patched #gem to generate mipmaps, may become unnecessary with upstream changes (so I can do it on the Pd patch level instead of in the C++).

Struggled with getting pix_snap2tex working, so ported it to gemframebuffer, but that looked bad (#WebGL does antialiasing only for the main output, not FBO). Turns out it was something unrelated (bad define in my GLEW hack), and pix_snap2tex works great in the end.

WIll work on the audio today, needs more variation.