examples without sdl

[aeosynth]

cargo build in user_input gives me an error:

  = note: /usr/bin/ld: cannot find -lSDL2
          collect2: error: ld returned 1 exit status

can we run the examples without using sdl, only using glutin?

edit: the tiled example works, user_input doesn't. so let me rephrase this to: fix the examples that currently need sdl