potential precision issues

[tcql]

trafficstars

I've run into some cases where corners disappear or lines bridge gaps, but they're not easily reproduced with visual tools.

It's occurred several times in my testing, but can't always get it to reoccur even when following the same steps, which leads me to believe numeric precision is causing the issues.

[tcql]

added test cases for this and #14 here: 052678f

[tcql]

I'm not sure this is fixed (or is a real problem) yet, I'll need to find more test cases