[videoinfoscanner] scan the entire subtree of path passed to scanner.

- fixes new files not getting picked up when more than 1 level down.
- fixes hashing never being used when scanning a single directory.
SlingboxLib: Fix alternative CSlingbox constructor

CSlingbox::CSlingbox(const char * szAddress, unsigned int uiPort /* = 5001 */) {
  // Call default constructor
  CSlingbox();
  ...
}

"CSlingbox();" - object is created and immediately removed.
Therefore with CSlingbox(const char * szAddress, unsigned int uiPort /* = 5001 */) class members will not be initialized.
[release] bump to 14.0 beta1
[pvr] fix unnecessary creation of new CPVRChannel instances
[builtin] fix activatewindow if directory path differs

After #5081 the built-in "activatewindow" does not work if you stay for example in the video window and you want to activate the same window with a different path.
This fixes the issue by comparing the directory path of the current active window with the given directory path of activatewindow.
[AE] Rename ActiveAEResample to ActiveAEResampleFFMPEG
[AE] Move utility functions to AEUtil
[AE] Add factory for AEResampler
[rbp] Hardware accelerated resampling

This replaces the format conversion, up/down mixing and resampling code from ActiveAE with a GPU accelerated version.
Should significantly reduce CPU when using paplayer or dvdplayer.

Requires updated firmware
[resamplepi] Add GPU accelerated option to resampling options
[darwin] - sync xcode project
[win32] - sync project
[PVR] bump add-ons
Add broadcastnow and broadcastnext to PVR.GetChannels (serialization of
CPVRChannel).
Bump JSON-RPC API version to 6.20.0
[visualizations] properly deinit presets dialog in order to avoid focus and scrollposition changes (fixes #15478)
Respect parent path decision when cleaning paths.

When cleaning the video library and a source containing TV shows was unavailable,
choosing to keep it only kept the source root, while subdirectories were
removed.
The result was that TV shows "disappeared".

This is fixed by checking if there's a decision for the parent path when
cleaning the path table.
Merge pull request #5522 from groth-its/jsonrpc-epgnow

JSON-RPC: Extend PVR channel details to be more convenient to client applications
[keyboard layouts] use English language names

Also added small comment to guide future contributors.
[configure] libflac is not a hard dependency now