Use different names for USB/CEC and Udev related threads

While debugging some rescanning issues, it helped to distinguish the different PeripheralBus threads. Since there is a limit to thread names, I had to make sure the name fitted into 15 characters.

This is part of a series of PRs: #2323 and #2541

Before:
```
xbmc.bin-+-{EPGUpdater}
         |-{EventServer}
         |-2*[{PVRClient}]
         |-{PVRGUIInfo}
         |-{PVRManager}
         |-2*{PeripheralBus}            <-
         |-{SoftAE}
         |-{TCPServer}
         |-5*[{XBPython}]
         `-8*[{xbmc.bin}]
```

After:
```
xbmc.bin-+-{EPGUpdater}
         |-{EventServer}
         |-2*[{PVRClient}]
         |-{PVRGUIInfo}
         |-{PVRManager}
         |-{PeripBusCEC}                <-
         |-{PeripBusUSBUdev}            <-
         |-{SoftAE}
         |-{TCPServer}
         |-5*[{XBPython}]
         `-8*[{xbmc.bin}]
```
added ActivateScreensaver to builtin functions
Merge pull request #2632 from ace20022/fix_null_pointer

[Fix] Possible NULL pointer dereference in DVDFactoryDemuxer.
Merge pull request #2624 from ScudLee/musicvideodashfix

Allow dashes in music videos on the first pass
[rbp/omxplayer] Fix audio volume jumps when switching tracks

When the global volume has been set low, and a sequence of tracks are being played, there are complaints of occasional jumps to full volume.
This is down to a race condition where the volume request can arrive at OMXAudio before it has been initialised.
The fix is simple, don't send the volume change until m_CurrentAudio.started.
[players] Fix dts time after seek
[rbp/omxplayer] Update media time sooner with online streams
Merge pull request #2641 from popcornmix/fix_volume_jump

[rbp/omxplayer] Fix audio volume jumps when switching tracks
Merge pull request #2625 from hmis/AirTunes_pts

Fix AirTunes pts accuracy
Rename our local copy of av_read_frame_flush to xbmc_read_frame_flush as suggested by elupus on PR2633.

That way it makes it clear the function is from xmbc and not ffmpeg.
[libdvd] - added missing patches
[Fix] http protocol options seekable=0 now finally works.
Merge pull request #2644 from ulion/fix_seekable_protocol_option

[Fix] http protocol options seekable=0 now finally works.
GUIFadeLabelControl: fix control being marked as dirty when label stays empty

If used infolabel will return empty string on first use, m_shortText will never be evaluated. If m_shortText is set to false control is marked as dirty so if used infolabel is empty control will be wrongly marked as dirty.
FIX: log spamming
DllAvCodec: map avcodec_encode_audio2
correct date formats. fixes #14286
Typo fix in README.raspberrypi
Merge pull request #2650 from robinbijlani/patch-1

Typo fix in README.raspberrypi
Merge pull request #2646 from koying/fixlogspamming

FIX: log spamming