Restore the full clipboard state after switching text

[TolikPylypchuk]

The ability to get clipboard data in all available formats before switching and then putting it back after switching should at least be investigated.

[TolikPylypchuk]

It appears that it's impossible to restore the full clipboard state on Windows as applications with custom clipboard formats can react to the clipboard being destroyed and will delete the advertised handles to it. I can at least try to restore several well-known formats instead.

[TolikPylypchuk]

I've decided to postpone this feature until after 4.2 so that 4.2 can be released in the nearest future.

[TolikPylypchuk]

I've decided not to implement this feature for now. Saving and restoring non-text formats may involve copying large amounts of data which will significantly slow down text switching (and the system overall).