Edit Mesh: Fix some problem with new implementation

- Add manual depth offset to vertices and edges.
- Revert to plain edge decoration.
- Fix active edge coloring.
- Remove active face display if not in face selection mode.
- Add wide line support.

source/blender/editors/include/BIF_glutil.h

@@ -106,6 +106,7 @@ void set_inverted_drawing(int enable);
 void setlinestyle(int nr);
 
 /* own working polygon offset */
+float bglPolygonOffsetCalc(const float winmat[16], float viewdist, float dist);
 void bglPolygonOffset(float viewdist, float dist);
 
 /* **** Color management helper functions for GLSL display/transform ***** */