feat(library/blast/forward): opportunistically delete dead hypotheses
feat(library/blast/forward): opportunistically delete dead hypotheses

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