Change travis warning flags to -Wall -Wextra
Change travis warning flags to -Wall -Wextra

-W is the 'old' name for -Wextra

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