Compile fixes for new Graphviz version.
Correct line intersection checking for evaluation.
Merge branch 'master' of github.com:skieffer/ortho

Conflicts:
	libdunnartcanvas/canvas.cpp
Merge branch 'master' of github.com:skieffer/ortho
Widen the non-overlap gap to avoid nodes between gridlines.
Grid size slider and fix slider click events.