don't request streams when opening the demux, it is always done soon after
when the DMX_SPECIALID_STREAMCHANGE packet comes in
[pvr] use Refresh() instead of Update() to refresh directory listing

To get rid of the default value for strDirectory in Update() and to gain control of whether we want to clear the cache or not, this will use Refresh() instead of Update() in all PVR windows to refresh the directory listing.
[pvr] cleanup: removes forgotten commented code block
[addoncallbacks] check key is non-null before use
Merge pull request #4334 from Jalle19/requeststreams

Remove a superfluous call to RequestStreams()
Merge pull request #5032 from jmarshallnz/addon_callbacks_nonnull

[addoncallbacks] check key is non-null before use
fix build when HAL is enabled
Merge pull request #5031 from xhaggi/pvr-window-refresh

[pvr] use Refresh() instead of Update() to refresh directory listing
WindowXML::LoadXML: fix checking result of CXBMCTinyXML::LoadFile()