refactor(library/logic/connectives): mark theorems used to prove 'decidable' theorems as transparent
refactor(library/logic/connectives): mark theorems used to prove 'decidable' theorems as transparent

if we don't this, then 'if-then-else' expressions depending on theorems
such as 'and_decidable', 'or_decidable' will not compute inside the kernel

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