A fix for rendering coincident polygons or lines.

Specifically fixed edge visibility which I had implemented
incorrectly. Trying to move the lines closer when you need
to move the polygons back instead.

Change-Id: I2a210e20287d4881767fe445afdde3458dfbac3b
Merge topic 'coincident_fix' into master

a7460ef0 A fix for rendering coincident polygons or lines.