Replace legendre_eval() with three term recurrence formula.
Replace legendre_eval() with three term recurrence formula.

Evaluating higher-order Legendre polynomials using the three term
recurrence is more accurate than the scheme that was used previously,
especially for higher orders. I'm not sure about execution speed, but
we can always revisit this if it somehow shows up in the timings.

capitalaslash/libmesh,dschwen/libmesh,jwpeterson/libmesh,dschwen/libmesh,hrittich/libmesh,capitalaslash/libmesh,dschwen/libmesh,roystgnr/libmesh,hrittich/libmesh,BalticPinguin/libmesh,libMesh/libmesh,dschwen/libmesh,capitalaslash/libmesh,libMesh/libmesh,roystgnr/libmesh,jwpeterson/libmesh,capitalaslash/libmesh,BalticPinguin/libmesh,capitalaslash/libmesh,capitalaslash/libmesh,libMesh/libmesh,hrittich/libmesh,jwpeterson/libmesh,BalticPinguin/libmesh,hrittich/libmesh,hrittich/libmesh,dschwen/libmesh,jwpeterson/libmesh,BalticPinguin/libmesh,roystgnr/libmesh,libMesh/libmesh,libMesh/libmesh,roystgnr/libmesh,jwpeterson/libmesh,roystgnr/libmesh,hrittich/libmesh,dschwen/libmesh,hrittich/libmesh,BalticPinguin/libmesh,hrittich/libmesh,dschwen/libmesh,roystgnr/libmesh,jwpeterson/libmesh,roystgnr/libmesh,capitalaslash/libmesh,BalticPinguin/libmesh,BalticPinguin/libmesh,hrittich/libmesh,libMesh/libmesh,jwpeterson/libmesh,dschwen/libmesh,jwpeterson/libmesh,BalticPinguin/libmesh,roystgnr/libmesh,libMesh/libmesh,capitalaslash/libmesh,libMesh/libmesh