http://leagueoflegends.wikia.com/wiki/Gangplank
Remove Scurvy does not remove Ignite, the damage reduction from Exhaust, any 'airborne' crowd control effects (pulls, knock-backs and knock-ups) or Malzahar's Malefic Visions.
Not sure why Malz is mentioned there are his Visions are CC-less without a handy dandy Rylai's, but nah, GP can't un-airborne himself with a daily dose of vitamin C. He can, however, unsuppress himself, which is the normal uncleansable CC.
Stasis is a very unique case, as it's normally intended either for transitional effects (Sion's passive animation, Guardian Angel, etc.) or trade-off situations (Zhonya's rendering you unable to do anything but unable to be hurt.) Applying it to enemies is...unorthodox, but making Stasis effects cleansable would invite a whole host of wacky interactions.
Plus, no oranges for you.