Keyboard modifier state synchronization

[m1k1o]

Synchronize CapsLock, NumLock and ScrollLock with client.

Only from Mouse and Keyobard events can we get users state. That's why state is synchronized one user first enters canvas with mosue.

Known isues:

• ScrollLock is not working at all when pressing in Linux canvas. Bus synchronization works. Maybe is not used and could be just ignores.
• Sometimes ist works in reverse. Hard to tell when, just... sometimes it bugs. I couldn't find what causes this bug. Needs propper testing.