Fixed several annoyances with halo render + unified render (bug 1989+2382)

- Maximum faces/halos per pixel was 500, which wasn't correctly applied in
  all cases, causing errors in AA
- Moved maximum up to 1000 now
- made halos become clipped away from filling in buffers when behind a
  solid face. That saves a lot of rendertime!

Unified remains weak with halos...

source/blender/render/intern/include/zbufferdatastruct.h

@@ -71,7 +71,6 @@ RE_APixstrExt  *addpseA(void);
  * Add an object to a zbuffer entry.
  */
 void insertObject(int teller,
-/*  				  int opaque, */
 				  int obindex,
 				  int obtype, 
 				  int dist,