Quite a large one this time... but now we have:

Edges in Mesh
- adds automatic when you use creases. For other situations; call the
  void make_edges(Mesh *me) in mesh.c. Of course, once in editmode the
  edges are automatically recreated.
- in F9 buttons you can add/remove edges too
- both for Mesh and DisplistMesh, so it speeds up drawing quite some in
  wireframe
- render for edges can't work... edges have no material nor tface nor col..
  so here still the faces are rendered in wire

Creases in Subsurf
- based on the code by Chris McFarlen
- main changes is that now edges are used, saving quite some data in file
- use SHIFT+E in editmode to set edges-sharpness. values go from 0-1
- in F9 buttons you can set draw-crease mode. It draws now blended from
  wire color to edge-select color (as provided in Theme)

Known issue: setting sharpness on 1 cube (subdiv 2) gives weird results
with some values... Chris, can you check?

Further; code cleanups, changing 0 in NULL when needed, no warnings, etc etc

source/blender/render/intern/source/renderHelp.c

@@ -37,6 +37,7 @@
 #include <stdlib.h>
 
 #include "DNA_mesh_types.h"
+#include "DNA_meshdata_types.h"
 #include "BLI_arithb.h"
 
 #include "render.h" 

source/blender/render/intern/source/rendercore.c

@@ -40,6 +40,7 @@
 #include "BKE_utildefines.h"
 
 #include "DNA_mesh_types.h"
+#include "DNA_meshdata_types.h"
 #include "DNA_image_types.h"
 #include "DNA_object_types.h"
 #include "DNA_camera_types.h"

source/blender/render/intern/source/texture.c

@@ -55,6 +55,7 @@
 #include "DNA_object_types.h"
 #include "DNA_lamp_types.h"
 #include "DNA_mesh_types.h"
+#include "DNA_meshdata_types.h"
 #include "DNA_material_types.h"
 #include "DNA_image_types.h"
 

source/blender/render/intern/source/zbuf.c

@@ -45,6 +45,7 @@
 
 #include "DNA_lamp_types.h"
 #include "DNA_mesh_types.h"
+#include "DNA_meshdata_types.h"
 
 #include "radio_types.h"
 #include "radio.h"  /* needs RG, some root data for radiosity                */
@@ -2193,8 +2194,8 @@ extern unsigned short usegamtab;
 void abufsetrow(int y)
 {
 	APixstr *ap, *apn;
-	float xs, ys;
-	int x, part, a, b, zrow[100][3], totvlak, alpha[32], tempgam, nr, intcol[4];
+	float ys;
+	int x, part, a, zrow[100][3], totvlak, alpha[32], tempgam, nr, intcol[4];
 	int sval, tempRf;
 	unsigned short *col, shortcol[4], tempcol[4], sampcol[16*4], *scol;