Add regression test to expose bug fixed in previous commit.
Add regression test to expose bug fixed in previous commit.

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

soonhokong/lean,johoelzl/lean,eigengrau/lean,dselsam/lean,sp3ctum/lean,fgdorais/lean,rlewis1988/lean,dselsam/lean,avigad/lean,fgdorais/lean,fpvandoorn/lean,levnach/lean,Kha/lean,eigengrau/lean,soonhokong/lean,Kha/lean,leodemoura/lean,digama0/lean,soonhokong/lean-osx,leanprover-community/lean,c-cube/lean,leanprover-community/lean,rlewis1988/lean,htzh/lean,UlrikBuchholtz/lean,c-cube/lean,leanprover-community/lean,soonhokong/travis_test,soonhokong/lean-osx,rlewis1988/lean,leanprover/lean,rlewis1988/lean,digama0/lean,fpvandoorn/lean2,johoelzl/lean,UlrikBuchholtz/lean,soonhokong/travis_test,codyroux/lean0.1,Kha/lean,leodemoura/lean,eigengrau/lean,dselsam/lean,javra/lean,leodemoura/lean,codyroux/lean0.1,leanprover-community/lean,dselsam/lean,leanprover/lean,soonhokong/travis_test,avigad/lean,javra/lean,soonhokong/lean-windows,leodemoura/lean,soonhokong/lean,soonhokong/lean,avigad/lean,fpvandoorn/lean,levnach/lean,c-cube/lean,soonhokong/lean-osx,htzh/lean,levnach/lean,fgdorais/lean,leanprover-community/lean,UlrikBuchholtz/lean,levnach/lean,soonhokong/lean-windows,javra/lean,soonhokong/lean-windows,dselsam/lean,fgdorais/lean,johoelzl/lean,soonhokong/lean-osx,htzh/lean,digama0/lean,UlrikBuchholtz/lean,sp3ctum/lean,fgdorais/lean,UlrikBuchholtz/lean,leanprover-community/lean,dselsam/lean,eigengrau/lean,avigad/lean,leodemoura/lean,htzh/lean,c-cube/lean,soonhokong/lean,javra/lean,soonhokong/lean-windows,johoelzl/lean,Kha/lean,fpvandoorn/lean,rlewis1988/lean,sp3ctum/lean,javra/lean,soonhokong/travis_test,sp3ctum/lean,soonhokong/lean-osx,eigengrau/lean,levnach/lean,avigad/lean,avigad/lean,htzh/lean,fpvandoorn/lean2,digama0/lean,johoelzl/lean,fpvandoorn/lean2,leanprover/lean,rlewis1988/lean,fpvandoorn/lean,leanprover/lean,digama0/lean,c-cube/lean,Kha/lean,digama0/lean,codyroux/lean0.1,fpvandoorn/lean2,Kha/lean,leanprover/lean,sp3ctum/lean,fpvandoorn/lean,soonhokong/lean-windows,fpvandoorn/lean,fpvandoorn/lean2,codyroux/lean0.1,leodemoura/lean,johoelzl/lean,fgdorais/lean,leanprover/lean