The revised patch from Leon for new particle effects.

New is that objects can have a force field, and Meshes can even deflect
(collide) particles. This is in a new sub-menu in Object buttons F7

The full instructions where on the web, Leon mailed it me and I will put
it in CMS tomorrow. For those who like to play with it now, here are demo
files:

http://download.blender.org/demo/test/

Quite some changes where in the integration though... so previous created
particle deflectors will not work. Changes to mention now are:
- gravity is renamed to 'force field'
- force field and deflector options are in Object now, not in Mesh
- the options also have its own struct, doesnt add to Object by default
- force fields are possible for all object types, but only work on center.
  So empty objects are typical for it.

Work to do:
- add draw method in 3d win to denote forcefield objects
- check on the UI (panel with different size?)
- add 'recalc' button in deflector panel

source/blender/src/glutil.c

@@ -87,10 +87,13 @@ void sdrawXORline(int x0, int y0, int x1, int y1)
 
 void glutil_draw_front_xor_line(int x0, int y0, int x1, int y1)
 {
+	glReadBuffer(GL_FRONT);
 	glDrawBuffer(GL_FRONT);
 	sdrawXORline(x0, y0, x1, y1);
 	glFlush();
+	glReadBuffer(GL_BACK);
 	glDrawBuffer(GL_BACK);
+	
 }
 
 void sdrawXORline4(int nr, int x0, int y0, int x1, int y1)