#668 Zero length lines in SVG not rendered correctly

[Paul Flo Williams]

When converting SVG files to PNG (for example), GM correctly renders zero-length path segments if the linecap is round or square, but it doesn't render zero-length line segments.

The attached SVG contains a few zero-length line segments and I have converted the second one to a zero-length path to demonstrate the difference in treatment.

Version: 1.3.38.