Removed some window state, added multithreaded capability.

Right now the code's in an ugly state, just messed around with it until
it worked, which is defined to be the situation where a red circle gradually
gets larger as it is updated by a thread separate from the main GUI.

Cleanup commit to come.
Cleanup commit for basic multithreaded GUI.

This commit cleans up the last patch, which introduced a multithreaded GUI that
updated a red circle (which was enlarged gradually).

Among the things cleanup were (1) usage of STM when unnecessary and (2) GTK
methods leaking into the main module.