virtual vertices aren't correctly cleaned up after feature modification

[elemoine]

To reproduce the problem, go to < http://www.openlayers.org/dev/examples/modify-feature.html>, then

• draw a polygon
• select it for modification
• drag a virtual vertex
• unselect the polygon
• zoom out

A vertex of the polygon is rendered on the vector layer.

[crschmidt]

I can't reproduce this in FF2 on Mac...

[crschmidt]

I was wrong -- I forgot to zoom in/out to see this.

[tschaub]

better vertex management

[tschaub]

Virtual vertex needs to either get removed from the layer. This can be done directly, or it can be shifted to the vertex array for removal there. I like the second because this is more literally what we are doing - converting a virtual vertex into a regular vertex.

In addition, I've removed the redundant vertices from linear rings. We were adding duplicate vertices with no effect. No need for the extra call to the renderer.

Tests pass in FF. Please review.

[crschmidt]

Agreed on both changes.

[tschaub]

(In [5623]) Proper handling of virtual vertices so we don't leave them on the layer. r=crschmidt (closes #1230)