GL: Allow window & overlay widgets to setup the camera using start-dl.
The user must compile start-dl and it will be shared by all widgets that
use it.
GL: Remove widget translation from eventContextDispatch() mouse positions
since pick-point takes screen coordinates.
m2: Support Qt 5 in Linux and Windows scripts.
Add boron_eval1() to public interface.
m2: Fix broken linker command on Linux when multiple Qt libraries are used.