[omxplayer] Add option to choose omxplayer/dvdplayer automatically

On Helix dvdplayer is pretty usable on the Pi, and is the only option
in some use cases:

omxplayer does not support external sound cards (USB or I2S)
omxplayer does not support dvd menus
omxplayer does not support software codecs

Expecting the user to choose the right player is not ideal,
so make the switch automatically for these three cases.
[rbp] Make cachemembuffersize default depend on memory size
[confluence] Use animated gif as a cheaper working spinner
[experimental] Disable quiet-noise generation
[settings] Experiment: Report DESKTOP resolution in video settings
Added some vc_tv_* functions that were missing in DllBCM.
Added private utility function to map a float display aspect, to the respective SDTV_ASPECT_* enum value.
Changed SDTV resolutions to be treated similarly to HDMI resolutions in SetNativeResolution. This means that the SDTV interface is powered up and set to the right mode.
Added methods SuspendVideoOutput() and ResumeVideoOutput() to CRBP class, which can be used to power down the Raspberry PI's video interface, and restore it at a later point.
PowerManager (and its IPowerSyscall instance) now gets called from CApplication::OnKey() and can process and suppress key presses. This is a requirement to implement a virtual sleep state.
Added CPowerSyscallVirtualSleep class, which acts as a base class for devices that have no native standby mode, and need to fake it in some way.
Added power management support for the Raspberry Pi. Since it doesn't support true standby, we fake it by turning video on or off, and ignoring remote inputs during the standby phase.
[power] hack - don't kill lirc or cec
[power] hack - wake on any action
[power] hack - Make suspend toggle suspend state
[power] Add back in powerdown and reboot
[cec] Don't suspend pi on tv switch off - it can't wake up
[rbp] Resume video output on startup
omxrender: Hacks to reduce GUI rendering rate when playing video
egl: Treat unknown display aspect ratio as square pixel