unordered_map in copy_nodes_and_elements
unordered_map in copy_nodes_and_elements

This shaves 10% or 20% off of my debug mode run times and it should be
a win in optimized modes as well.

roystgnr/libmesh,90jrong/libmesh,svallaghe/libmesh,hrittich/libmesh,libMesh/libmesh,90jrong/libmesh,jwpeterson/libmesh,90jrong/libmesh,hrittich/libmesh,jwpeterson/libmesh,svallaghe/libmesh,capitalaslash/libmesh,libMesh/libmesh,svallaghe/libmesh,dschwen/libmesh,hrittich/libmesh,pbauman/libmesh,dschwen/libmesh,jwpeterson/libmesh,dschwen/libmesh,libMesh/libmesh,90jrong/libmesh,dschwen/libmesh,hrittich/libmesh,capitalaslash/libmesh,balborian/libmesh,libMesh/libmesh,balborian/libmesh,dschwen/libmesh,svallaghe/libmesh,roystgnr/libmesh,balborian/libmesh,90jrong/libmesh,jwpeterson/libmesh,capitalaslash/libmesh,jwpeterson/libmesh,svallaghe/libmesh,svallaghe/libmesh,dschwen/libmesh,giorgiobornia/libmesh,balborian/libmesh,pbauman/libmesh,BalticPinguin/libmesh,pbauman/libmesh,svallaghe/libmesh,capitalaslash/libmesh,roystgnr/libmesh,90jrong/libmesh,pbauman/libmesh,jwpeterson/libmesh,giorgiobornia/libmesh,capitalaslash/libmesh,balborian/libmesh,BalticPinguin/libmesh,BalticPinguin/libmesh,BalticPinguin/libmesh,roystgnr/libmesh,capitalaslash/libmesh,giorgiobornia/libmesh,giorgiobornia/libmesh,libMesh/libmesh,BalticPinguin/libmesh,libMesh/libmesh,svallaghe/libmesh,dschwen/libmesh,hrittich/libmesh,balborian/libmesh,BalticPinguin/libmesh,jwpeterson/libmesh,capitalaslash/libmesh,dschwen/libmesh,roystgnr/libmesh,balborian/libmesh,BalticPinguin/libmesh,capitalaslash/libmesh,BalticPinguin/libmesh,hrittich/libmesh,pbauman/libmesh,pbauman/libmesh,jwpeterson/libmesh,pbauman/libmesh,giorgiobornia/libmesh,giorgiobornia/libmesh,balborian/libmesh,90jrong/libmesh,hrittich/libmesh,giorgiobornia/libmesh,balborian/libmesh,svallaghe/libmesh,hrittich/libmesh,giorgiobornia/libmesh,pbauman/libmesh,libMesh/libmesh,pbauman/libmesh,balborian/libmesh,roystgnr/libmesh,libMesh/libmesh,90jrong/libmesh,90jrong/libmesh,roystgnr/libmesh,giorgiobornia/libmesh,hrittich/libmesh,roystgnr/libmesh