dirname: in impl, make behavior for '/' fs root agnostic of host platform
dirname: in impl, make behavior for '/' fs root agnostic of host platform

Heather/coreutils,ebfe/coreutils,wimh/coreutils,Heather/coreutils,kwantam/coreutils,uutils/coreutils,ebfe/coreutils,kwantam/coreutils,Arcterus/coreutils,jbcrail/coreutils,uutils/coreutils,tempbottle/coreutils,keunwoo/coreutils,jbcrail/coreutils,kevgeniy/coreutils,uutils/coreutils,wimh/coreutils,kevgeniy/coreutils,keunwoo/coreutils,tempbottle/coreutils,Arcterus/coreutils