fix(frontends/lean/pp): display private 'internal' names in a human readable way
fix(frontends/lean/pp): display private 'internal' names in a human readable way

Signed-off-by: Leonardo de Moura <7610bae85f2b530654cc716772f1fe653373e892@microsoft.com>

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