Add a new test for EDGEFLAGS point attributes.

Edge flags can be used to choose which edges of a polygon must
be drawn when polygon is drawn in wireframe.
The test shows a square which is actually made of 4 visible edges
of 4 triangles.

Change-Id: I02f4ce2f5d55a564d49dc5b6a23ccec9f2a19148
Merge topic 'add_edgeflags_rendering_test' into master

7b869762 Add a new test for EDGEFLAGS point attributes.