adderall.dsl: Add a #? reader macro

The #? macro generates a new LVar, one we don't care about. Use it as
'#?_' to write discardable LVars.

Signed-off-by: Gergely Nagy <algernon@balabit.hu>
adderall.extra.zebra: Solution to the Zebra puzzle

Signed-off-by: Gergely Nagy <algernon@balabit.hu>