vnc led: Add SCROLL lock key to kbd_leds

This patch series tries to add support for LED state
extension to Qemu VNC server. The proposal has been sent
few days ago as link below:

This is just an initial implementation, and has not been
completely tested. To catch up Qemu 1.5 soft freeze, I'd
like to send it out to have your suggestion. Please let me
know if this seems like the direction we should be headed.

Your suggestions and comments are very appreciated!

Thanks

See http://lists.gnu.org/archive/html/qemu-devel/2013-04/msg01421.html

(cherry picked from commit 0bbfa6b70735cba7d8e03cfb8032c2f418bb66de)
(cherry picked from commit 52d868739dc320630d946698aacfefa25ad73c10)
(cherry picked from commit be5ac2badc60137be90206c7186077aa241750e8)