autotools: Gui split

This is the beginning of an autotools build-system refactor. My first step is to be able to create a common static lib for the binaries (console/qt/test) to link against, meaning that each of those will need its own entry-point object file.

This series gets rid of the QT_GUI define in favor of letting the build-system link in the proper startup file, and a global var to determine how the binary was started.

I've tried to match this project's formatting and general practices.