Splitscreen community co-op is highly broken

[vrad-exe]

The local splitscreen mode for community co-op maps that was added in one of the recent updates has a number of bugs (at least on Windows, but I don't see why this would be platform specific), making it borderline unusable.

• Quick play does not work, and will still prompt to invite a friend online
• The vote screen doesn't show up at the end of maps
• Skipping to the next test chamber crashes the game
• Exiting to the queue and selecting a different map prompts to invite a friend, instead of starting the new map in splitscreen. To make it work you have to exit the queue screen and press the local splitscreen button again.

Additionally, the queue screen should probably have a different window title when you're in splitscreen mode to make that more clear. If you don't want to have to worry about new translations, reusing the existing #Portal2UI_PlaySplitscreen ("PLAY SPLITSCREEN") should work well enough.