SSU: Fix partial acks not being sent when there are no 'gaps'.
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I2P Address: [http://git.idk.i2p]
Workaround the bug on the sending side for pre-0.9.49 routers by sending fragments in reverse order.
Bug introduced in commit 9c4558d8 Sep 20 2014. This partially reverts that commit. Reported by and adapted from a patch by zlatinb
Base32 Address: [http://7qeve4v2chmjdqlwpa3vl7aojf3nodbku7vepnjwrsxljzqipz6a.b32.i2p] Onion Address: [http://47ggr2fa3vnwfyhvgskzdmr3i32eijwymxohtxsls45dulmriwxszjad.onion]