Fix memory leakage in python bindings

The python bindings generated by the groovy code generator contain a reference counting bug which results in a memory leak whenever a std::vector is converted to a python list.  The following member functions are affected:

* xbmcvfs.listdir
* xbmc.Player.getAvailableSubtitleStreams
* xbmc.Player.getAvailableAudioStreams
* xbmcgui.Control.getPosition
* xbmcgui.Dialog.browse
* xbmcgui.Dialog.browseMultiple

The reference counting bug occurs because PyList_Append() increments the reference count of the item, so the caller needs to call Py_DECREF() because it no longer owns the object.

This bug is especially problematic when running the Watchdog Service Addon since it may result in frequent calls to xbmcvfs.listdir, and each call can leak many kilobytes of data when listing directories containing many files.
[DVDInputStreamNavigator] allow fallback to root menu call if title menu call fails (like VLC)
[DVDInputStreamNavigator] allow to return from "endless" loop of NOPs
use FF_LEVEL_UNKNOWN by default (prevents some common mismatches in
ParsePacket which triggers reopening of streams)
Do not allow non-content stream types to extend the format context's duration as this
affects the UI and therefore seek capabilities.

DVB subtitle/teletext streams are private streams (stream type 0xBD) and may have their
own timebase or PTS values that are widely different than video stream's,
or not set properly. Regardless of any handling of such cases in FFmpeg, XBMC shouldn't
extend play duration unless an actual content stream has passed it's "end".
[win32/libnfs] - downgrade to 1.3.0 because of issues with 1.6 on windows
(not able to reproduce - not able to fix)
AE: make sure sink suppports required samplerate for AC3 and DTS
paplayer: avoid blocking in OpenFile, call QueueNextFile instead
[omxplayer] Always enable timestamp fifo mode.

hints.ptsinvalid is only set for h264 in avi files. However it also can affect any videos with B frames in any container
(we have reports of mp4 and mkv stuttering because of invalid pts values).

To solve this we always enable the timestamp fifo mode, and the gpu treats this as an optional flag, and falls back to non-fifo timestamp
mode if the variance of that timestamp stream is better.
[PiSink] Report all hdmi samples rate as supported. Required for passthrough
FIX: [touch] workaround double-click in file manager
Use NULL from cstddef

This fixes build when GIT_REV is not defined.
ffmpeg: dxva2_h264: set the correct ref frame index in the long slice struct

The latest H.264 DXVA specification states that the index in this
structure should refer to a valid entry in the RefFrameList of the picture
parameter structure, and not to the actual surface index.

Fixes H.264 DXVA2 decoding on recent Intel GPUs (tested on Sandy and Ivy)
ffmpeg: dxva2_h264: add a workaround for old intel GPUs

Old Intel GPUs expect the reference frame index to the actual surface,
instead of the index into RefFrameList as specified by the spec.

This workaround should be set when using one of the "ClearVideo" decoder
devices.
[dxva] Add support workaround for Intel H.264 VLD, no FGT, ClearVideo decoder.
[dxva] Prefer standard Microsoft H.264 device instead of Intel H.264 VLD, no FGT (ClearVideo).

This fix h264 decoding with refs > 11 on recent Intel GPUs (SNB/IVB). The latest Intel drivers for IVB/Haswell already has no support old Intel H.264 VLD, no FGT (ClearVideo) device, so this actually needs for SNB and older.
[nfo] remove unused variable
[music] ensure we grab the path of albums and artists before looking for .nfo files - fixes #14964
[music] set album/artist path at the top of the Show*Info() methods rather than inside it to save querying the path multiple times
[music] fix embedded thumbs going missing once you leave a directory. fixes #14637