refactor(util/rb_tree): remove optimization that creates problems for some compilers
refactor(util/rb_tree): remove optimization that creates problems for
some compilers

levnach/lean,javra/lean,rlewis1988/lean,levnach/lean,digama0/lean,leanprover-community/lean,fgdorais/lean,avigad/lean,leodemoura/lean,fpvandoorn/lean,digama0/lean,soonhokong/lean-windows,soonhokong/lean-windows,leanprover/lean,johoelzl/lean,soonhokong/lean-osx,dselsam/lean,leanprover/lean,johoelzl/lean,leanprover-community/lean,fgdorais/lean,fgdorais/lean,UlrikBuchholtz/lean,fgdorais/lean,levnach/lean,soonhokong/lean-windows,soonhokong/lean,Kha/lean,sp3ctum/lean,fpvandoorn/lean,johoelzl/lean,leanprover/lean,eigengrau/lean,soonhokong/lean-osx,fpvandoorn/lean2,levnach/lean,c-cube/lean,avigad/lean,soonhokong/lean-osx,fpvandoorn/lean2,soonhokong/lean,c-cube/lean,dselsam/lean,fpvandoorn/lean2,leanprover-community/lean,rlewis1988/lean,javra/lean,avigad/lean,rlewis1988/lean,leanprover-community/lean,htzh/lean,digama0/lean,UlrikBuchholtz/lean,soonhokong/lean-windows,UlrikBuchholtz/lean,htzh/lean,htzh/lean,digama0/lean,Kha/lean,Kha/lean,Kha/lean,UlrikBuchholtz/lean,dselsam/lean,fpvandoorn/lean,sp3ctum/lean,fpvandoorn/lean,fpvandoorn/lean,eigengrau/lean,eigengrau/lean,fpvandoorn/lean,htzh/lean,rlewis1988/lean,avigad/lean,c-cube/lean,dselsam/lean,johoelzl/lean,Kha/lean,soonhokong/lean,fpvandoorn/lean2,sp3ctum/lean,johoelzl/lean,soonhokong/lean-osx,sp3ctum/lean,javra/lean,fgdorais/lean,soonhokong/lean-windows,htzh/lean,Kha/lean,fgdorais/lean,levnach/lean,leodemoura/lean,dselsam/lean,javra/lean,soonhokong/lean-osx,rlewis1988/lean,johoelzl/lean,leanprover/lean,eigengrau/lean,avigad/lean,rlewis1988/lean,javra/lean,digama0/lean,eigengrau/lean,leodemoura/lean,c-cube/lean,leodemoura/lean,leanprover/lean,soonhokong/lean,leanprover-community/lean,c-cube/lean,digama0/lean,leanprover-community/lean,fpvandoorn/lean2,avigad/lean,sp3ctum/lean,UlrikBuchholtz/lean,soonhokong/lean,leodemoura/lean,leodemoura/lean,leanprover/lean,dselsam/lean