Patch from Benjamin Spencer:
Patch from Benjamin Spencer:

Add get_node_index() method to Elem class.

Given a pointer to a Node, returns the local index to that node
for this element.

git-svn-id: ffc1bc5b3feaf8644044862cc38c386ade156493@5332 434f946d-2f3d-0410-ba4c-cb9f52fb0dbf

certik/libmesh,certik/libmesh,certik/libmesh,certik/libmesh,certik/libmesh,certik/libmesh,certik/libmesh