Fix warnings when configured with --disable-optional.
Fix warnings when configured with --disable-optional.

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