[#7925] use frozensets for faster O(1) checking of file extensions
[#7925] use frozensets for faster O(1) checking of file extensions

apache/allura,heiths/allura,lym/allura-git,apache/allura,heiths/allura,heiths/allura,lym/allura-git,lym/allura-git,apache/allura,heiths/allura,lym/allura-git,apache/allura,lym/allura-git,heiths/allura,apache/allura