• [API Change] Can specify clock granularity in engine settings.
• [BUGFIX] Pacer uses fixed clock granularity. Since the change on 2018-04-09, it is not necessary to try to approximate the next tick time in the pacer: it can use fix clock granularity specified by the user.
• [BUGFIX] Do not tick constantly before handshake is done.
• [BUGFIX] Do not exit tick prematurely: reuse packet with ACK. Even if we cannot allocate more packets, we could still be able to write o one already allocated.
• [BUGFIX] Do not schedule pacer if there are no lost packets.