optutils.SetNodeSucessors improvement
Sorry for all this spam, I just sort of believe in these 0.999¹⁰⁰⁰ things, you know.
This patch speeds up optutils.SetNodeSucessors by a lot and the entire -O3 compilation very slightly (0.02%). Speed up is mainly from the fact that average SetNodeSucessors ends up not using BreakContinueStack at all (90% of the time in my codebase) so efforts of setting up and tearing down some fancy structure for it often go in vain.