Returns whether this character has completed the quest with the given name. See 'immh new_spec_quester' for more details on quests. Quests can be added or removed by calling set with this function.
For example, to check whether %a has completed the quest 'frolic', the command would be
if(did_quest(%a,'frolic'),
To set %a as having completed 'frolic', it would be
set(did_quest(%a,'frolic'),true)