Fix compilation on gcc 5
Fix compilation on gcc 5

Fixes #782

Eigenstate/msmbuilder,brookehus/msmbuilder,mpharrigan/mixtape,dr-nate/msmbuilder,rafwiewiora/msmbuilder,msultan/msmbuilder,msultan/msmbuilder,peastman/msmbuilder,mpharrigan/mixtape,rafwiewiora/msmbuilder,Eigenstate/msmbuilder,peastman/msmbuilder,msmbuilder/msmbuilder,mpharrigan/mixtape,peastman/msmbuilder,cxhernandez/msmbuilder,msultan/msmbuilder,Eigenstate/msmbuilder,brookehus/msmbuilder,dr-nate/msmbuilder,cxhernandez/msmbuilder,msmbuilder/msmbuilder,peastman/msmbuilder,brookehus/msmbuilder,Eigenstate/msmbuilder,msmbuilder/msmbuilder,peastman/msmbuilder,cxhernandez/msmbuilder,mpharrigan/mixtape,Eigenstate/msmbuilder,rafwiewiora/msmbuilder,dr-nate/msmbuilder,mpharrigan/mixtape,msultan/msmbuilder,rafwiewiora/msmbuilder,msmbuilder/msmbuilder,brookehus/msmbuilder,msultan/msmbuilder,dr-nate/msmbuilder,rafwiewiora/msmbuilder,brookehus/msmbuilder,cxhernandez/msmbuilder,cxhernandez/msmbuilder,msmbuilder/msmbuilder,dr-nate/msmbuilder