Carmack's reverse revert

This gets rid of the workaround added because of the creative patent.
This also gets rid of 2 unneccesary draw calls per shadow volume.

Thanks for labeling the patent workaround with a comment, John :)

Signed-off-by: Daniel Morsing <daniel.morsing@gmail.com>

neo/renderer/draw_common.cpp

@@ -1143,16 +1143,14 @@ static void RB_T_Shadow( const drawSurf_t *surf ) {
 		return;
 	}
 
-	// patent-free work around
 	if ( !external ) {
-		// "preload" the stencil buffer with the number of volumes
-		// that get clipped by the near or far clip plane
-		qglStencilOp( GL_KEEP, tr.stencilDecr, tr.stencilDecr );
-		GL_Cull( CT_FRONT_SIDED );
-		RB_DrawShadowElementsWithCounters( tri, numIndexes );
-		qglStencilOp( GL_KEEP, tr.stencilIncr, tr.stencilIncr );
+		qglStencilOp( GL_KEEP, tr.stencilIncr, GL_KEEP );
 		GL_Cull( CT_BACK_SIDED );
 		RB_DrawShadowElementsWithCounters( tri, numIndexes );
+		GL_Cull( CT_FRONT_SIDED );
+		qglStencilOp( GL_KEEP, tr.stencilDecr, GL_KEEP );
+		RB_DrawShadowElementsWithCounters( tri, numIndexes );
+		return;
 	}
 
 	// traditional depth-pass stencil shadows