Default ctor and valid() method for values
Default ctor and valid() method for values

aclements/libelfin,tempbottle/libelfin,aclements/libelfin,aclements/libelfin,abenkhadra/libelfin,aclements/libelfin,tempbottle/libelfin,abenkhadra/libelfin,abenkhadra/libelfin,abenkhadra/libelfin