header: Add printf attribute checking with gcc.
header: Add printf attribute checking with gcc.

aleksandr-vin/cmock,nuumio/cmocka,tyc/cmocka,Odie/cmocka,chadversary/cmocka,nuumio/cmocka,clibs/cmocka,tyc/cmocka,wingyplus/cmocka,JonathonReinhart/cmocka,akikoskinen/cmocka,aleksandr-vin/cmock,linuxmaniac/cmocka,jschmidlapp/cmocka,dsch/cmocka,jamesmunns/CMocka,jamesmunns/CMocka,Odie/cmocka,Odie/cmocka,wingyplus/cmocka,jhrozek/cmocka,JonathonReinhart/cmocka,nuumio/cmocka,dsch/cmocka,lsjostro/cmocka,VladimirTyrin/cmocka,jhrozek/cmocka,chadversary/cmocka,lsjostro/cmocka,jschmidlapp/cmocka,jhrozek/cmocka,linuxmaniac/cmocka,VladimirTyrin/cmocka,jschmidlapp/cmocka,tyc/cmocka,clibs/cmocka