New FileStream test for very large sparse files is a bit slow
New FileStream test for very large sparse files is a bit slow

Most of the time taken is deleting the file when done, but it can be
speeded up a little by not closing and reopening the file, as then the OS
is not forced to commit to disk.

jgfoster/Dolphin,jgfoster/Dolphin,jgfoster/Dolphin,objectarts/Dolphin,dolphinsmalltalk/Dolphin,shoshanatech/Dolphin,dolphinsmalltalk/Dolphin,shoshanatech/Dolphin,blairmcg/Dolphin,blairmcg/Dolphin,objectarts/Dolphin,jgfoster/Dolphin,blairmcg/Dolphin,dolphinsmalltalk/Dolphin,dolphinsmalltalk/Dolphin,blairmcg/Dolphin,shoshanatech/Dolphin,shoshanatech/Dolphin