Blender Git Loki

Fix T32214: Wireframe edge select fails with verts behind the view

This resolves a long standing bug in edge selection
(picking, circle, box & lasso).

Now when one of the edges vertices fails to project into screen space,
the edge is clipped by the viewport to calculate an on-screen location
that can be used instead.

This isn't default as it may be important for the on the screen location
not to be clipped by the viewport.