we can now kill and wait for the slider watcher subprocess that we spawned.
However, it will have a subprocess itself, the lipc-wait-event process.
That one currently stays alive until it finally sends something.
The sources can now conditionally compile emulation code
for the e-ink framebuffer and input events.
It uses SDL for doing that, so you need this installed
if you want to use emulation (you do not need it if you're
only compiling for the e-ink device).
This allows for rapid testing of new code.
