Fix for the use_hidden_preview setting in SpaceNode. The application of this flag to new nodes got lost during merges at some point. Also is now in the python node.add_node operator as well as the C function.

git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@55506 954f8c5b-7b00-dc11-b283-0030488c597c