Add Debug builds to travis
Add Debug builds to travis

Makes 'all clang' builds enable the tidy pass

steveschnepp/OpenApoc,FranciscoDA/OpenApoc,ShadowDancer/OpenApoc,FranciscoDA/OpenApoc,Istrebitel/OpenApoc,ShadowDancer/OpenApoc,Istrebitel/OpenApoc,pmprog/OpenApoc,pmprog/OpenApoc,steveschnepp/OpenApoc,FranciscoDA/OpenApoc