README.linux update
README.ubuntu update
[pvr] invalidate all items if window becomes invalid
[pvr] fix ctor args for CGUIMessage to re-broadcast observer notify messages
Merge pull request #5038 from xhaggi/pvr-invalid-window-on-channel-switch

[pvr] invalidate window if using fast channel switch
Merge pull request #5011 from uNiversaI/readme

Readme updates
[addons] fix null ptr dereference in GetTranslatedString