Two additional fixes for node-tree + texture paint:

- "need exec" flag was cleared in wrong tree for preview renders
  (it should clear it in the copy, i did in original).
  This fixes projection paint on images with previews open
- Previews for nodes were copied always, now only for previews 
  invoked by node editor itself.

source/blender/blenkernel/intern/node.c

@@ -2815,14 +2815,14 @@ bNodeTree *ntreeLocalize(bNodeTree *ntree)
 	/* end animdata uglyness */
 
 	/* ensures only a single output node is enabled */
-	ntreeSetOutput(ntree);
+	ntreeSetOutput(ltree);
 
 	for(node= ntree->nodes.first; node; node= node->next) {
 		
 		/* store new_node pointer to original */
 		node->new_node->new_node= node;
 		/* ensure new user input gets handled ok */
-		node->need_exec= 0;
+		node->new_node->need_exec= 0;
 		
 		if(ntree->type==NTREE_COMPOSIT) {
 			/* move over the compbufs */

source/blender/editors/render/render_preview.c

@@ -983,6 +983,7 @@ static void shader_preview_updatejob(void *spv)
 	ShaderPreview *sp= spv;
 	
 	if(sp->id) {
+		if(sp->pr_method==PR_NODE_RENDER) {
 			if( GS(sp->id->name) == ID_MA) {
 				Material *mat= (Material *)sp->id;
 				
@@ -995,7 +996,7 @@ static void shader_preview_updatejob(void *spv)
 				if(sp->texcopy && tex->nodetree && sp->texcopy->nodetree)
 					ntreeLocalSync(sp->texcopy->nodetree, tex->nodetree);
 			}
-		
+		}		
 	}
 }