Evdev Input Optimizations and MDNS fixes

This should probably be two pull requests. Oh well.

First change:
I'm using the EV_SYN event to trigger sending input events. This is the same thing Limelight Android does. The advantage of this is that it significantly cuts down on the number of input events sent over the network. Rather than 2 per mouse move or analog stick move (1 for X axis and 1 for Y axis), it will only send a single event with both axes present. In my testing moving the analog sticks around on a Pi B+ 800MHz, I saw a baseline of 50% CPU usage with no input. On 1.0, I saw 65% usage during my test. On master with my changes, I saw only 55%.

Second change:
I fixed mDNS PC discovery which was broken because the discovery agent was never started. I also applied the debugging level before starting discovery to prevent the INFO logs from the discovery agent. I made a change in limelight-common to fix a hang that would occur after using mDNS to find the PC.

Please pull limelight-common and update the submodule.