3d -- further fixes for 3d lines that end in an arrow.
3d -- further fixes for 3d lines that end in an arrow.

DrXyzzy/smc,tscholl2/smc,DrXyzzy/smc,tscholl2/smc,tscholl2/smc,DrXyzzy/smc,sagemathinc/smc,DrXyzzy/smc,sagemathinc/smc,tscholl2/smc,sagemathinc/smc,tscholl2/smc,sagemathinc/smc