Increase USB and CEC rescan interval to 5 seconds

In one of my investigations to see why XBMC performance is so bad (even when idle) I found one of the threads (in my case PeripheralBusCEC) scan a big sysfs tree recursively. On the 1Ghz AppleTV 1 device this would be about 2% of the CPU *every* second. For the USB thread we luckily have Udev events, but for CEC it is using sysfs polling which is quite expensive. It would be better to make use of Udev as well for CEC (where available) however 5 seconds should be fine for everyone.

In my own builds I even brought it down to 30 seconds. Which means 29 seconds of reduced CPU usage.

The CEC polling probably should be more restricted to specific sysfs sections, or preferably use Udev as well, when available.

PS XBMC needs a special idle-state where it can turn down these expensive threads to make sure hardware can go into deeper sleep states. Especially for devices that doesn't do suspend for various reasons this is a requirement. (The ATV1 device for instance gets warm even when idle) If we can combine display-sleep with low-power states and a less expensive main-loop, that would be already quite an improvement without needing a complete refactoring of the code.
settings: add description textbox (ID 6) to CGUIWindowSettingsCategory
remove unused LinuxTimezone.h include
settings: fix timezone-related settings visibility and default values
settings: fix loading of platform-dependent settings definition files
settings: allow appliance.xml to overwrite runtime-dependent visibility conditions and default values
Merge pull request #2637 from dagwieers/rescan-interval

Raise USB and CEC rescan interval to 5 seconds
Merge pull request #2775 from Montellese/settings_description

settings: add descriptions area to CGUIWindowSettingsCategory
[rbp/omxplayer] Remove unused variable m_pTempOverlayPicture
[rbp/omxplayer] Remove unused Pause/Resume functions

These should be implemented with clock component
[rbp/omxplayer] Remove call to OMXLateCount that will be removed
[rbp/omxplayer] Remove unused clock code
Merge pull request #2799 from popcornmix/cosmetics

[rbp/omxplayer] [Cosmetics] Remove unused code
[cleanup] moves IGUIContainer into a separate include and drops the GUIBaseContainer.h include from GUIViewControl.h.
[rbp/omxplayer] Support planar float format audio directly

The update to ffmpeg1.2 has produced a significant performance hit on the Pi when decoding multichannel audio without passthrough.
This is because (most) audio codecs now output planar floating point, rather than interleaved S16 samples.
OpenMax/GPU can handle interleaved S16 samples directly, whereas the floating point planar samples get converted with swr_convert.
This is a slow operation, and a quick profile showed it to be taking about 150MHz of ARM CPU when using 6 channel audio.

I've added support on GPU for a new floating point planar format in audio_decode component.
This PR makes this format also supported for sending audio to the GPU.
The GPU now also handles the 6->8 channel padding so the UpMix() function is no longer required,
which may improve performance compared to pre-ffpeg1.2 version.

This PR requires recent GPU firmware. (384946 or later).
vdpau: fix segfault caused by uninitialized member
[rbp/omxplayer] Merge with current dvdplayer

To make spotting differences between omxplayer and dvdplayer easier in the future,
this is a pretty slavish copy, including dvdplayer's whitespace and header file includes.
You now get a pretty clean diff between dvdplayer.cpp/dvdplayer.h and omxplayer.cpp/omxplayer.h
Merge pull request #2796 from Montellese/settings_initialization_fixes

settings: initialization fixes
Merge pull request #2815 from FernetMenta/vdpaufix

vdpau: fix segfault caused by uninitialized member
[osx] changed, move videoplayer.usevda into darwin_osx.xml and nuke a vda dyload define